There are two major airports in Bangkok - Suvarnabhumi and Don Muang. The first one is the main international airport and you are likely to arrive there while travelling from Europe, Australia or the U.S. Don Muang is the home hub for Air Asia, the excellent low cost airline that I would truly recommend for local travel. Local travel means not only domestic flights but also flights to the neighboring countries.

From Suvarnabhumi there are two recommended options. YOu can take the ARL (Airport Rail Link) which is inexpensive, fast and reliable way to get downtown or to interchange with BTS (Skytrain). So the choice depends on the area where you stay and also on the number of persons. Three and more are probably better off by taxi, with little or no price difference. If you are more than four you would look for a minivan. For ARL follow the sign to the underground floor -it is pretty straightforward. For taxi you can also follow the signs and then queu for them on the ground floor. The other option (faster) is to go up to the departure level where dozens of taxis bring travellers and then head back empty. YOu will get one within seconds and most probably at a good price. The general note for taxis is Bangkok - it appears today that better than negotiating the price beforehand it is a better option to go for a "taximeter" and pay according to the posted amount. In the rare occassion when the taxi driver refuses to switch the taximeter on, simply get off and grab the next one.

With the abocve said, you already know pretty everything. BTS and MRT (the underground) are easy and fast to use. Buses may be a littly bit confusing for the beginner. Taxi are not expensive. Tuk-tuks are rather the folklore - not much cheaper then taxis with a higher risk involved in case of accident. Would recommend them for very short trips only. Motorbike taxis are the cheapest, take one person at a time and present certainly an experience comparable with bunjee jumping or similar.