Having lived in London nearly 30 years, it always astonishes me how little I use anything other than the Northern Line. Each Tube line has it’s own feel, every bit as much as each neighbourhood has it’s own vibe. I’ve lived (briefly) south and north, but the oldest dirtiest Tube line is the one that feels mine.
Getting about on public transport is incredibly easy, Trains, both undergound and overground run frequently as do the many buses. We have a car for when we drive out to see relatives and are feeling especially lazy visiting friends but for visitors a car will be a total liability.
Perhaps the biggest surprise for me out and about was the convenience of the commuter boats that chug up and down the Thames from Putney to Greenwich.
I wanted to sail past the Houses of Parliament so started out at Vauxhall, changed over at Embankment to a second boat that ran up to Greenwich. Changing over at North Greewich is simple and making my way back down to Embankment to link back up with the Northern Line.
One of the best thing about the boat routes, is how many tourist attractions lie along the journey. For anyone with kids, visiting the Maritime Museum and Cutty Sark at Greenwich is a great start (or end) to the journey. Pulling into the wharf at Tower Bridge to see the Tower of London is an amazing experience, followed by stops at Tate Modern (and also the Globe Theatre the re-created Elizabethan theatre created by Sam Wannamaker) and the London Eye for the best views across London.
Most of the major tourist sites are easily accessible. If practical, walking the streets is one of the best ways to get a feel for the place.