Taxis at Bangkok Airport

My mom asked me how to catch a cab at Bangkok International Airport and I am reprinting my advice here.
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The best way to catch a taxi from BKK airport is to go up to the Departures level (second floor) and catch one that’s dropping off somebody or is driving by.
The second best way is to go to the taxi stand out on the curb on the Arrivals level (first floor) and get a slip of paper that ensures you will get a metered taxi (although I haven’t seen an unmetered taxi for years). It will automatically cost 50 baht more to do this, and even though that’s not very much money, the taxis on the Arrival level are notoriously old and dirty (this makes a huge impact when the A/C is cranked and the windows are rolled up the whole time).
The absolute worst thing to do is to agree on a fare inside the airport. Some cabbies will try to help you with your bags to try and get you in their cabs, especially if you look like a noob, but refuse them. They charge up to ten times the normal fare, which is still under twenty bucks, but still….
There is a map of the airport here: Bangkok International Airport