The Open Guide to London: the free London guide

Every platform at every Tube station obviously has a way out. However, all Tube platforms are not the same. If you see a Where To Alight notation on a page about a Tube station, riding to Tube at the point indicated should cause you to end up next to the exit from the platform when you arrive at your station. You can also actually buy a Tube map with this information on it.

For longer journeys, you might be more interested in Where To Get On to be in the least-crowded part of the train.