What should I do after buying an airline ticket?

Just to repeat Relaxed's excellent answer. Yash, the process is:

(1) PURCHASE a ticket. These days, that is almost always online at say Expedia, or over the phone. You'll get some sort of purchase code, like XFD123HHC

Note that these days, it's usually confusing since there is both an EXPEDIA code AND a code from the AIRLINE! (Possibly even more than one airline.) So, write all those down, or if you prefer print it out from your computer.

(2) CHECK-IN. At the airport, you "check-in". This means you give them your code numbers, and you show them your passport, and you give them your luggage. In return they give you your boarding pass.

Note, as it says you give them your luggage. But any small "carry-on" items, you just keep in your hand.

So, "check-in" is all about getting your boarding pass.

Boarding passes almost always look like this:

(3) Next, AFTER checking in, you go through security. You have to show them your boarding pass and also your passport again. They scan you and your small "carry on" items. You then enter the departure area of the airport. Only people who are actually flying, can go there - you have to say goodbye to your family as you enter the security check point.

Now - you go shopping! :) There are always shops in the departure area. In any large airport, it is like a shopping mall. Once again, the only people in the departure area are people who are actually flying - they have a boarding pass in their hand. (And of course people like police, shop-keepers etc who have special passes to be in the "passengers only" area.)

(4) Finally you board the airplane. This happens at the gate. You have to give them your boarding pass and show them your passport. At the gate they remove and keep the large part of the boarding pass (on the left in the image above) and you keep the small part (on the right). The only reason you keep the small part is to remember your seat number. (if you happen to drop it or lose it it is no big deal.

So after shopping, you all stand around at the gate. Eventually they will say "Now boarding, your flight 247". You all line up and go through the gate - as I explain, they take your boarding pass, you show your passport, and they give you the small tear-off piece. At that instant you do and must walk straight on to the plane (down the walkway) and that's you on the plane. (You cannot go back to the shops, or anywhere else, after that.)

To recap:

(1) purchase online. Give: credit card number, Get: reservation number(s).

(2) at the airport: check-in. Give: reservation number(s) + luggage. Show: passport. Get: boarding pass.

(3) at security. Show: boarding pass + passport. Get scanned (you and your carry-on bags).

You're now in the "departure area" which is often like a mall. Passengers only.

Wait until you hear "Flight 247 now boarding at gate 44B..."

(4) at the gate. Show: boarding pass + passport. Walk on to the plane and sit down, you cannot return to the departure shopping now.

Notes:

(A) traditionally, you only got your seat assignment at the moment of checkin. ie on the actual day, at the airport. However these days...on the web, after you buy the ticket, typically you can click and actually choose your seat, so that's good. (In fact, nowadays, most airlines now have a con where you can then pay a little more for a "better" seat.)

(B) at most big airports, in fact, you can "check-in" - so, leave your luggage with them - right on the road where you get out of the taxi. Sometimes you do that and you ALSO have to then check-in at the main check-in counters inside; sometimes all the check-in is handled at the roadside.

(B2) To add more confusion, these days you can often check in using a machine that looks like an ATM. Instead of having to line up to talk to a human at the check-in counters, you line up to use a little sort of machine; they might have a row of ten or so of these machines. You just type in your numbers and it prints out the boarding pass for you (see image above). Note that in this case you have to put your bags "somewhere", sometimes a person comes and gets it, sometimes you use the roadside system, sometimes you then go to another counter etc. Personally if it was my first time I'd just go to a human at a check-in counter! I would not use the "automatic machine" nor the "roadside check-in".

(B3 !!) And note that these days, you sometimes do not need to check-in at all! If you have only hand baggage, in some cases you can "check in online." You do that at home even before going to the airport. I would avoid this if you are new!

(C) note that check-in is the part where you "have to wait" - those are the long lines you see at airports. it can often happen you have to wait for an hour in the line. some people like to arrive very early, to be the first to check in, so you don't have to wait. note that by doing that you can get a better seat (BUT that does not apply so much these days, as explained above: you can usually choose your seat in advance, online.)

the wait to go through security CAN BE very long, particularly say in the US. the wait to actually board is no big deal, you all just line up and go on the plane.

I hope it helps you, or some other readers! more and more people are flying for the first time, so, enjoy.

It definitely needs to be noted that some airlines these days require the flyer to present the original credit card used to book the ticket upon check-in too. This is an attempt to reduce internet fraud. Check with your airline if this is the case, as the airlines are generally super strict if they follow this policy (no credit card, no flight, no exceptions!)

When you buy a ticket online (or otherwise) you get a reservation code. Normally one could print out a confirmation email just so you have that code on paper for reference. With that code on the date of the flight you will go to the airport to the counter of the airline that sold you a ticket and a lot of airlines nowadays provide electronic means of checking-in for the flights so once you check in and check your bags in if any you will get your boarding passes printed and with them go through security to the gates and then onto the plane.

There are other methods that are allowed for check-in such as online check-in which is open 24 hours before the flight in most cases, which will let you print the boarding passes and take them with you and go straight to security unless you have to check your bags and so on.

If flying to South Africa or even simply transiting through South Africa and you are taking minors (anybody under the age of 18) with you, there were some recent regulations passed in the country which will be very relevant to you:

All minors have to travel with full unabridged birth certificates (i.e. showing both parents). Both the named parents have to be travelling together with the minor. If only 1 parent is travelling with the minor, an affidavit authorising the travel from the other parent is required along with a copy of their passport/ID. If a minor is travelling with neither parent then affidavits from both parents are required and the copies of their passports/IDs. The only way out of the "affidavit from other parent" requirement is if the travelling parent has single-custody of the minor in question (and can show the paperwork) OR if the travelling parent has the death certificate of the other parent. If any of these documents are not in English, a sworn translation into English needs to be supplied too.

This is a rather ill-thought-out policy to try stop child trafficking and child traffickers using South Africa as a hub. Unfortunately it has been passed into law so there will not be much you can do if you are lacking in documents. If you are flying into or through South Africa your airline should have warned you by now already and check your documents at check-in. These laws kick in on the 1st October 2014.

The process in summary:

1. Buy the ticket online or from a travel agent. You will get a proof of purchase (either as paper receipt or an attachment to your email). You need to bring this with you to the airport.

2. Once you arrive at the airport, you need to obtain a boarding pass in order to pass security and board the aircraft.

   To obtain the boarding pass, you have to present yourself, proof of reservation and some form of identification to the airline. If you have luggage that is too big (or contains items not allowed in the cabin) you can give this to the airline to be checked in and carried in the cargo area of the aircraft.

   Typically you walk to the check in desk (these usually open 2 hours before the actual flight time; although at some larger airports major airlines offer checkin up to 24 hours before the flight departure) and hand your receipt from step 1, along with your passport to the agent. They will check your eligibility to fly, ask you some basic security questions, and give you one or more boarding pass(es) depending on the nature of your journey.

   These days, thanks to automation many airlines are offering self-service check-in kiosks. You approach a kiosk and scan your passport, which recognizes your name and then prints the boarding pass.

   Some airlines allow you to check in from their mobile applications directly, even bypassing any kiosks.

   In these situation if you self check-in, you can also walk upto specially marked stations and deposit any luggage that you want to check-in (that is, not carry with you in the cabin).

3. Once you have obtained the boarding pass - you and any luggage you wish to carry to the aircraft must pass security checks before you can enter the secure area of the airport, from where you will board your aircraft.

   Security requirements vary greatly between airports, however the most common requirements are:

   a. Remove your laptop / tablet from your bag and present it separately for scanning. Sometimes, they may ask you to turn on the laptop.

   b. Remove your coat, belt and (sometimes your shoes) and place them on a tray for scanning separately.

   c. Any liquid/gels should be presented in a clear plastic bags for separate inspection. Normally, any liquids you are carrying (such as water bottles) are not allowed and the personnel will ask you either finish your drink or discard it.

   Depending on the airport you may walk through a metal detector, a particle detector (looks like a booth and you stand in it with your arms raised), be subject to a manual search, or all of the above. The security process can be a bit stressful if this is your first flight.

4. Once you have passed security, you may be required to clear immigration. You should walk up to the officer and present your passport and your boarding pass. At some airports (such as the US) there are no exit formalities at all and for some flights (such as those within the Schengen zone) may not require any passport controls.

5. Once past security and immigration you are in the transit area of the airport. You can relax and do some shopping or grab a bite to eat before your flight. Be mindful of your boarding time and plan to be at the gate before this time.

6. Once you arrive at the gate, your boarding pass will be scanned and you may be asked to show your passport as well. From here, you simply board your plane and your flight starts.

7. Once you arrive at your destination, simply follow the signs for "Baggage Claim" or "Immigration / Customs".

8. As you are on an international flight, you may first be required to go through immigration. Simply present your passport to the immigration officer; they may ask some questions or request some additional documentation from you (such as a copy of your hotel reservation where you will be staying). Be polite and answer their questions.

9. After immigration, you are ready to collect your luggage - which will arrive on a series of moving belts. You may also be subject to a customs check; where they inspect your luggage and ask you questions about what you are carrying.

10. Once past customs - congratulations - welcome to the new country!

I wanted to add one factor missing from other answers.

After you buy ticket from a travel agent, you should always immediately double-check following 4 things by either calling up the airline office OR by visiting manage my booking section on airline website.

1. Validity of the ticket (i.e. does the PNR number - last name combination exists in airline database)

2. Baggage allowance for individual flights in your journey (related Airline and Travel Agent disagree on baggage allowance, who do I need to resolve it with? )

3. [In case of connecting flights] will the baggage be through checked-in till the final destination? Some airlines may not have agreements with others for baggage transfer.

4. [In case of connecting flights] Will you get all the boarding passes when you check-in for originating flight or will you need to get BP for connecting flight at a transit transfer counter?