London Underground
Probably the most useful transportation method for the visitor to London is the tube, or Underground. The London Underground can be properly said to have begun in 1890 when an electrically-powered line was opened between King William Street and Stockwell. There are now 12 lines plus the Docklands Light Railway serving millions of travelers around London every day.
Although the tube will usually be the quickest and most inexpensive way of getting about London (that is, if you take advantage of the various discount passes available), be aware that the British Rail "above-ground" trains serve some areas of London better than the tube
Tickets - You can buy tickets either from automated machines or at a ticket window. You will need to keep your ticket until you have passed through the gates at your destination station. Be aware that ticket inspectors randomly police the Underground and can (and will) levy £10 fines for invalid tickets.
London Bus Transportation
Bus stop signs list the route numbers of the buses that stop there. If a bus is listed as "Request Only", then you must flag down the bus by raising your arm. If you don't, they won't stop.
Bus Pass
There are weekly and monthly passes good for unlimited travel on all London buses, but a better deal is the London Travelcard, good for unlimited travel on both the Underground and the buses. Travelcards can be purchased for 7 days or more at a time, but they require a passport sized photo.
Visitorcards are another option. They do not require a photo, and can only be purchased outside the UK. In addition to unlimited bus and Underground travel they include discount vouchers for many popular tourist attractions. Note that the Visitorcard is NOT valid for the Heathrow Express.
Minicabs
An alternative to the traditional black London taxis are minicabs. Despite the name, minicabs may offer space for more passengers than a black taxi; traditional London taxis can seat 5 passengers, while minicabs seat from 4 (most common) to 7 people. These cabs are unmarked, and cannot be hailed on the street like a black taxi; minicabs must be called for by telephone from a Licensed Private Hire Operator. Your hotel staff, waiters, or host should have a telephone list of licensed operators.
Docklands Light Railway (DLR) - The DLR runs an independent driverless service to the newly developed Isle of Dogs. A recent extension to the DLR runs under the Thames to Greenwich and beyond to Lewisham.
The DLR links to the London Underground at Tower Bridge, Tower Gateway, Canary Wharf, and Bank stations, and zone fares are the same as on the tube. However, there are a series of passes good only on the DLR. For example, the "Docklander" costs just £2.50 and allows unlimited travel on the DLR, but is only valid after 9:30AM. The DLR runs a 24-hour information line at 7918 4000.
Suburban Trains - Some areas of London are better served by trains than the tube, notably the northern suburbs. The North London Link stretches from Richmond across northern London to North Woolwich. Another useful rail service travels from Hampstead Heath to Kew. Often these suburban trains are cheaper than similar tube trains and leave the traveler closer to popular tourist destinations.