If anyone from out of town needs navigational help / advice on dealing with our truly crap public transport system, mail me with where you are trying to get from (and back to). Or post here.
I'm a nerd about this stuff - happy to help.
Some general tips
www.tfl.gov.uk
This has a route planner (click on the 'advanced' options so you can enter time/date of travel)
Also live travel information about tube lines that have broken. DON'T freak out if you look at it before friday and it tells you most of the tube lines are shut. There's a strike on, but it finishes thursday night.
Don't hire a car
Buses tend to get snarled in traffic, so don't use them for longer stretches - tube or main line train works best.
Sorry if I'm being patronising - I'm just always embarassed when I go to other cities and realise how damn EASY everything is!