The best way to get around London is by using the public transportation system.
Most areas have a local tube station.
The Tube is one of the best mass transit systems in the world and can be taken to most parts of the city. With the Travelcard, you can go anywhere just about any tourist would want to go, all day long, as many stops as you like. If you arrive at Heathrow or Gatwick airports, you may want to consider buying a multi-trip pass and take the Tube into town. Instead take a taxi or arrange for a service to pick you up. Once in the city you can get around very easily via the subway or buses.