To see the best (and worst) times to visit, please read our reviews of our recommended places to stay
The BTS sky-train has turned getting around Bangkok from a hot and sweaty nightmare into a cool, calm dream. It's the best way of linking the Sukhumvit area (commercial and embassy district) with the river at Saphan Taksin (access to wats and other monuments using river taxis). It's fast, regular and best of all it's air-conditioned.
The newer subway MRT is equally efficient but the stations are less well placed for general tourism. It's open from 5am to midnight, with trains running every 3-6 minutes.
For shorter distances, hail a tuk-tuk (open-sided three-wheeler) at least once, for the experience, or take a motorcycle taxi - but be prepared for fumes. Metered taxis can be flagged down everywhere. Ignore calls from stationary ones outside your hotel; they pay protection and pass the cost on to you. Insist the driver turns on the meter. Don't plan on driving yourself unless you know the city well.
The city buses are of little interest to most visitors to Bangkok, being slower and less fun than other transport.
Longtail boats whizz up and down the main river (Chao Phraya) and the smaller canals. Larger ones act like buses on certain canal routes, the smaller ones like taxis on a private-fare basis.
There are also larger river boats plying the main stretch of the Chao Phraya between Saphan Taksin bridge (south) and Ratanakosin (north). Some offer a live commentary of the wats and hotels en route. Many riverside hotels have their own courtesy boats.
If you want to get around in style, book at Chakrabongse Villas and you can use their private launch - decked out in wood and white leather - to zip up and down the river in speed and comfort. We motored upstream to Ko Kret island (flower farms, markets) in less than 30 mins.