If you arrive to Bangkok by way of Don Mueang International Airport, you may need a taxi to get to your hotel. After immigration and customs you descend an escalator to the arrival/departure area. You will see many taxi counters with employees directing you to their counter. Many of them are flat fee counters which are definitely more expensive than you need to pay. To use the meter taxis, walk to the very far left of the arrival departure area (when you are facing the building exits). You will see bright yellow signs with explanations of cost and fees. This is the cheapest way to get into Bangkok from the airport by taxi. Approach the yellow counter and tell the staff where you want to go. If you are not sure on pronunciation, have a print out of the hotel reservation. This should have the address and they will tell the driver.
My recent trip I told the taxi driver not to take the tolled highway. The trip only cost me 260 Baht with the 50 Baht surcharge. If I were to take the tolled highway, I would be responsible for the tolls, one for 70 Baht and the other for 50 Baht. The flat fee places quoted me 800 Baht.