London Underground (Londoners call it The Tube) is the quickest way of getting around London. The Underground has 12 lines, and covers 253 miles of track. Trains are fast, modern but in rush hours very crowded. The Tube is highly recommended for tourists, because in easy way they can visit many places in one day without traffic jam.
London Transport bus system provides over 6,800 scheduled buses, which are operated by independent operating companies. Buses are used for local journeys and by night. You can buy ticket from bus driver (only in Central London its impossible) or pre-purchase it from ticket-machine. Travel by London bus is also interesting because You can see there famous big double-decker red buses.
Tickets for London Transport are very expensive, especially for tourists. For single travel by bus you have to pay 2 pounds. Single The Tube tickets are more expensive but when you plan to use underground many times you should think about Travelcard for one or three days. For more information and ticket prices you should visit London Transport site.
Very popular in London are London Black Cabs. Maybe...