Arriving

If you plan to take a metered taxi, ask for small notes for your taxi when you exchange currency. The exchange booths are familiar with the request, will do so willingly and give you a good supply of small bills.  Many taxi drivers either do no have small change, or will tell you they don't hoping you will let them keep a large note/bill to avoid a problem or delay.

DO NOT use the offered LIMO/Taxi services offered by the Touts, who swarm around you once you leave the secured area, as they will rip you off. After you have your Thai Baht continue to the arrivals hall exit and join the queue for a taxi outside the building. The taxis and buses leave from the same floor as you arrive. There is a kiosk where you tell staff which hotel/where you want to go and you get a piece of paper with the Taxi number. Keep the paper in case of problems. Tell the driver to take the toll/express way, you will need to give the driver 65 Baht for the Tolls. There is also a 50 baht service charge, notice of this is stamped on the form. If possible get the name of the hotel you are going to in Thai as whilst they have a large list of places not everything is on there and English is not spoken well.

Most hotels in the Sukhumvit, Silom area should cost you about 200 - 250 Baht on the meter + 50 Baht airport tax for the taxi and should take about 30-60 minutes depending on the day and time of day.

Departing

Departing is even easier.

Get your taxi from your hotel to the airport. Plan to arrive about 2 hours early for domestic and 3 hours for international flights (This is the airlines recommendations).  The Taxi should take about 40 - 60 minutes and cost about 250 Baht from most downtown hotels.

If you have leftover Thai Baht, you can spend it before entering passport control at the Family Mart convenience store on Level 4(one level below departures). Prices are actually the same as in the city, which is a real deal compared to the other stores in the airport. Great place for delayed travellers to grab a snack. Remember that no liquids are allowed past security checkpoints.

Many of the gates can take a good walk to reach so it is a good idea to get there before the boarding time on your ticket.