Tips to avoid forgetting a bag

Put everything which isn't physically attached to you in one place. You're less likely to leave all your luggage behind than forget one item, so it's a bad idea to have your gloves are on the seat opposite, your small bag in the overhead rack, and your suitcase in the luggage store at the end of the corridor.

Attach numbered tags to each bag. Then all you need to remember is the total count or attach the highest +1 to your keychain and count.

You can get 50 from Amazon for ~$10. Key Tags with Ring, Numbered Id Tags

You can easily make your own with standard luggage tags and numbered stickers you would use on a mail box.

Each person has a bag or a couple of bags for which they are responsible. So when they start walking they count (one, two or at most three items) and one or (when traveling as a couple) two people do an overall count.

You have to be really careful to do it really every time, as you noticed one hurried departure and forgetting to count or check is enough to go wrong.
And start when you walk out of your home. My mother one year forgot the case with all the linens needed for a two week family holiday. Luckily she found out at the local station when the taxi driver got the cases from the boot, and there was enough time to go home and get it.

It is always good to restrict the number of items to no more than two per person, one big one and a small one you hold with you at all times.

One more thing, it is always better to be ready to get of a train well before you get into the station where you need to get off, so you have time to get your things together and have time to look around before you need to leave your seat area.
Just like the minute or so you have to wait before getting off a plane.

In addition to all the good ideas presented so far: You have to think of the one object you never fail to leave behind, that can be used to remind you to get the other objects you're usually not used to carrying.

For some people, that's their cell phone.

So if you attach Bluetooth Low Energy tags to your bags, you can have your cell phone/tablet blare an alert if it gets out of range of your bags (even if the sound is turned off on your phone and even if you don't have service in the country you're in). The built-in battery of a small BLE tag is supposed to last up to two years.

Honestly, I never tried this method. One of the drawbacks is that the Bluetooth range might be too good, so it might only start blaring once the train pulls away, not once you got out of the train (but I can't be sure about that, if the Bluetooth range has a sensitivity setting, maybe it can blare before you're too far away from your bags? That's probably true, but I'm just not sure about that part).

https://www.hongkiat.com/blog/bluetooth-tracking-devices/

https://thewirecutter.com/reviews/best-bluetooth-tracker/

Some of those tags apparently also have GPS builtin, but I think that's overkill.

One company took this concept of BLE tags even further. It can do all the stuff I described above and crowdsources the location of BLE tags even if you're completely out of range by using the phones of their other customers to collect the data.

For some people, it's their metro pass/ticket

So if you put your metro pass into the bag you're most likely to forget, and the station you're in requires your pass/ticket to exit the station, you won't be able to exit the metro if you don't have that particular bag. ;-)

I'm not sure if this is a feature or a bug. But in my case, it means I am paranoid about not losing that kind of ticket, so I double-check it often.

For some people, it's their keys

I personally have a lanyard on my keys and I tie my lanyard to my car dashboard, or sometimes I tie an obvious knot to it. This at least reminds me that I forgot something when I get home as I try to take my keys out of the ignition.

For some others, it's their coat, gloves, or scarf, especially in a super cold climate.

Here, you could just attach your coat to a part of your bag, or stuff each glove in a different bag.

For others still, it's their glasses, sunglasses, or hat (this will depend on the type of glasses, or even if there is any sun out there)

And for almost everyone, it's their current shoe(s)

This is the granddaddy of all reminders. Now I'm not suggesting that you do this on a train. But if it's a question of life or death, or if you know of new parents that are afraid to forget their baby/toddler in the back of the car (which can be extremely easy to do if the baby/toddler is sleeping, or there is a slight change in routine in the parent's life).

That new parent should take off one of their shoes when driving and leave that shoe in the back seat with the baby/toddler. And yes at least in the United States, driving without shoes on is perfectly legal. And personally, even if it was illegal, I would still do it even if it meant I wouldn't forget a toddler in the back of my car.

You can get pairs of tags. You attach one to your bag, and to other your person (or pair to your phone by bluetooth). When the two tags are separated, the tag on your bag will beep very loudly. They are generally called "anti-theft alarm tags", or "child proximity alarm"

This should remind you that you've wandered too far from your bag. However, they might sound if you put your bag in the carriage-end luggage rack, and take a seat in the middle of the carriage.

Plan ahead

Travel follows a similar pattern: You board, travel and then alight. Set some time aside to prepare for alighting. This will give you unhurried time to check your luggage as well as remembering you that there is a task which will require your full attention.

A few minutes as the train is pulling in will suffice.

Establish a routine

I really tend to lose stuff. So now whenever I am leaving a place I am checking whether I have my basics with me: phone, wallet, keys. I do it by tapping my pockets. This has become engrained and I started doing it automatically. Since I know I am quite distracted this tapping dance leads me to think: Is there anything else outside of the ordinary that I’m forgetting (coat, scarf, bag)? This prompts a visual inspection: I actively look around the area I was in.

Leave things in the way

Another trick I now use automatically: If I have a bag with me I’d wrap one of the handles/shoulder strap/whatever around a hand or leg in an unobtrusive way. Can’t forget it that way! Similarly I might put a bag in such a way that I have to stumble across it on my way out (e.g. between or under my leg).

I managed to leave behind

• Wallet with a Christmas payoff in it (big money as a kid) in a bar.
• A laptop bag on a plane with a laptop in it.
• A bag with many CDs and my CCG collection in it.
• Countless scarfs, gloves, hats, shoes (!), clothes (!?).

Use a mnemonic. Each morning when I leave the house I run my "W. K. Pig" check (wallet, keys, phone, ID, glasses)

I fare very well by having it hard-wired into my brain that whenever I get up in a place I do not inhabit, I visually scan that place for anything belonging to me. This does not only apply to seats in public transport, but also to restaurant seats, waiting areas, whenever I visit somebody, etc. The main exceptions are my own home and my workplace.

Of course, the more difficult thing is to hard-wire this into your brain. My ad-hoc suggestion for this (that I have not tried) is: Acquire a bunch of richly coloured handkerchiefs or similar cheap items. Whenever you are about to sit down at a place other than your home or workplace, put one on the seat. If you forgot to do this when sitting down, you can make good for it later. As you cannot feel or see it when sitting, you are bound to forget it – unless you visually scan the place after getting up. If you managed to survive a month or so without forgetting your item (or the routine), complete your training is.

Now, if you rely on a visual scan, there are a few precautions that you should take to make sure that the scan itself does not fail (some of which are already mentioned in the existing answers):

• Keep your stuff in one place.
• Avoid leaving in a hurry.
• If you have many items and expect that everything is crowded with items: Keep a list on a piece of paper. During your visual scan, you should notice how crowded everything is and this should remind you of the list.
• When travelling in a group and you are not the last person to leave, remind whoever will leave last to perform a visual check when your visual-check instinct triggers.
• If you have to place a piece of luggage where you would not see it with your visual check (e.g., a specific luggage section far from your seat, or under the seats), place a reminder item on your seat before you sit down.

The bluetooth/technology methods mentioned above help. But a simple, low tech solution would be to attach a carbiner on your belt and tie 550 cord from it to the bag if you must absolutely not forget the bag. If it's a backpack the cord won't even be noticeable most of the time. The benefit of this method is that no matter how tired you are on a long day of travel, the bag will be with you because the cord won't let you forget.

I always count the number of different things I have to carry after they are packed up. As an engineer numbers stick in my head much better than remembering items.

Also put them all in the same place with smaller ones on top.

And ALWAYS do a final sweep of the hotel room tearing the bed(s) apart.

Still forget things in the fridge every now and then.

This is a bit like Johns-305's and Three Diag's answers, yet I feel different enough to warrant its own.

Professionals often use checklists. You can, too.

Really, since this is about travelling: if you ever get a chance to talk to a commercial pilot (or even a private pilot), ask them if they'd be willing to fly without referring to their checklists, or even without having said checklists at all. Chances are pretty good that you will get some polite variation of "oh my effing dog no!". For many professionals, checklists are a way to make sure that a complex procedure is carried out correctly. These checklists can take many different forms, with perhaps commercial aviation checklists being among the most formal, and they can be made almost as formal or informal as one prefers. Towards the informal end, a shopping list or a recipe is a checklist. Really, there's no shame in referring to them.

While in the comfort of your own home, before leaving for your trip but after getting your luggage packaged, look over all of it. (At this point, it is presumably all in one place.) You might want to add tags to your bags, or make sure they are otherwise somehow distinctly marked. Then, write on a piece of paper "check to make sure the yellow, red and black bags and the backpack have been collected". (Substituting whatever method you use to tell them apart.) Bring this piece of paper with you. Whenever you do anything that involves moving your bags from one place to another, refer to this piece of paper, and confirm that you've got all the pieces of luggage in the correct new place.

This also works nicely for those items that you know you'll need on every trip (or most trips), yet for one reason or another keep forgetting, whether it's the toothbrush, the pair of fine shoes, or the kids' respective favorite toys. Write up a list, and before leaving, confirm to yourself that you've actually packed each item on the list, or made a conscious decision not to bring that particular item.

I travel a lot and used to have this problem. I don't have it any more, which is probably partly because of practice, but I believe the following things help:

• I never travel with more than two bags. The third bag is too easy to forget, and in any case, a big suitcase with good wheels is much more convenient to lug around than a collection of smaller bags. I usually also carry a small backpack for things I need to access while travelling, and/or wear a coat with big pockets for the same purpose.

• I avoid carrying unfamiliar bags. If you have a bag of shopping or some item that you're carrying with you, put it inside your suitcase or backpack instead of carrying it separately. The suitcase you always have with you is harder to forget than the random thing you picked up earlier in the day.

• I own brightly coloured, distinctive bags. A bright red backpack is much harder to leave on the seat than a black one.

I've had some success with setting an alarm to 5-10 minutes before I would need to leave the train. When the alarm goes off, I would collect all baggage, or at least mentally note their locations so i'll be ready when it is time to depart. Also, if you've estimated the time incorrectly (always err on the side of "too early"), you can just re-set the alarm. Using a quiet (vibration only) alarm is probably ideal so as not to disturb others.

If there are enough bags that you might forget one of them when noting their locations, using a checklist could help with that aspect of it.

The above strategies can all be done on a smartphone, but they don't require one.

Something I do as much as I can (althought it may seem weird) is to simply physically attach my bags to me. When I get on the train, I just get a string, tie it to my leg and go to sleep.

I do admit that this isn't quite always possible and can slightly restrain your movements, but you'd be surprised how often this can be done and how effective it is.

Physically attach the bags.

This is reminiscent of the famous idea of handcuffing a briefcase to the carrier. There is a physical attachment. (That is also the basic concept behind this answer (by "everyone").)

However, to expand on the concept:

We... were carrying quite a few bags with us, and somehow managed to leave one of them behind.

So you may have had too many bags to attach to you.

One solution that can work, is to attach the bags to each other.

If you have bags on wheels, then you can create your own "train" of bags as you move from one train to another.

I've seen this done (by my mother, and may have myself done) innumerable times. Just take a bag that has any sort of strap, and loop it through the handle or another strap of another bag.

There are some downsides to this method. Turning is difficult, and will basically require moving and/or adjusting each bag individually. However, it allows you to walk (potentially quickly) along the straight ways relatively okay. (Trying for too much speed, a.k.a. running, won't work.)

You may also detach the bags at various times. But when you approach a stop where you expect to move, you can ensure that you undo any temporary detachments. During the times that the bags are attached, you're unlikely to leave one behind due to forgetting.