If you don't have much to carry. The Airport Link is advisable. At the moment it only costs 15 baht from airport to city (Phayatai BTS) and vice-versa using the regular blue color train. But the Express, yung pula, it costs 100 baht pero non-stop naman from end to end.
If you must, though a bit pricy, use the Airport Limousine Service instead of the public taxi. I noticed that with the public taxi that we used before, medyo mabilis ang patak ng metro.

A friend once told me na, sabi ng taxi driver friend niya, isang trick daw nila is lakasan ang aircon. Nakakaapekto daw ito sa metro ng taxi. Have you heared about this?