London on public transport: what kind of tickets to use?

I'd recommend getting an Oyster Card.

You can order one in advance and have it sent abroad as well. It does take 5 to 8 work days for EU countries, and up to 12 for others. Note that only a few countries are supported -- mostly Schengen area, US, and select Asian countries. The card activation fee is 3 GBP, and you are also required to put in at least 10 GBP credit initially which you can later use.

This is by far the most flexible way to travel in London, especially since you'll be staying for more than a day or two. Check the website for conditions and fares.

The best feature is that you don't have to plan ahead your journeys for the day to get the cheapest daily fare overall (there is a ridiculous number of tickets you can purchase, depending on the number of zones you travel through, the time of the day, the phase of the moon etc.). In the end of the day, you will always be charged the least possible amount for all the journeys you made.

As far as travel passes go, there are a few which allow for unlimited journeys during a single day in one or more than one zones, and usually break even at around 5 trips.

You can recharge it online with a credit card, or at every tube station with cash/card. If this is your first visit, I'd say go for it.

Note that the price for individual fares is exactly the same if you purchase them directly, so if you are able to plan well, you might not need it at all.

The big advantage for me of the Oyster card was that I could top it up with a credit card. I found London very cash-oriented and never seemed to have cash when I needed it. The card could be refilled at any station using my Visa card.

I was staying with a family friend who keeps a card in the house for visitors - it had about 5 pounds on it when I arrived and I made sure to leave it a little fuller than that when I left. But on a future visit I wouldn't hesitate to buy one if I was staying a week or more. It takes the guesswork out of the process.

Well you'll want an Oyster card.

Now this works in three ways:

• Option A - Prepay. Top up a card, and then basically everything is half-price. Buses, trains, tram, etc.
• Option B - Bus pass. Unlimited bus use, all zones, for a week.
• Option C - Travel Card. This is unlimited bus use, and unlimited other transport just in specified zones (usually 1, 1-2, 1-3, 2-3, 1-4, or 1-6, although there are other options).

Given the length of time, I'd personally go for a Travel Card. It means you just don't need to worry after that. You can still top up with some extra prepay for when you go out of zones, or just use the bus for the bits that your zones don't cover. Easy.

You can read all about it on the TFL website.

It's worth noting that Heathrow is Zone 6. You could get a 1-4, which includes Richmond, and just put 5 pounds on pre-pay to cover your Heathrow rides. Also, you can buy and top-up Oyster cards at Heathrow airport, and return it to get your deposit back at the end. Heathrow and the tube work very well in tandem - assuming the tube is running, of course ;)

For more information, see another question we have on this.

As already mentioned in the accepted answer, instead of Oystercards you can use a bank or credit card which does contactless payments.

The cost will be taken from your bank or charged to your credit card, but in most casees it will work as an Oyster card, sometimes it even gives more advantages.

When the other answers were written it was relatively new and restricted but these days it is rather common and the options in public transport in London are broader than they used to be.