Be sure to either know the correct pronunciation of your destination, or have it written in Thai, as taxi drivers in Bangkok are notoriously bad at reading maps. Most hotels and guesthouses will happily write out addresses in Thai for you. While most drivers will recognize the names of tourist hot spots, even if grossly mispronounced, it is often difficult to properly pronounce addresses in Thai, a tonal language. If your mobile phone works in Thailand, it is sometimes useful to phone your hotel and ask the staff to speak to your driver in Thai. If you're pinching pennies or fussy about your means of transportation, you may wish to think twice before getting into one of the (very common) yellow-green taxis. They are owner-operated and of highly variable quality, and occasionally they have rigged meters. All other colors belong to large taxi companies, which usually enforce their standards better. On some routes, the driver will ask if he should use the Tollway - this will usually save a lot of time. You have to pay the cost at the toll booth (not in advance, and not at the end of the journey). Watch how much the driver really pays, he may try to keep the change.When getting out, try to have small bills (100 baht or less) or expect problems with change. Tips are not necessary, but are certainly welcome; most local passengers will round up, or leave any coin change as tip.