There is a sign clearly marked "transit passengers" - you cant miss it.
If you do exit the airport - just avoid the touts (some even very official looking, with bellboy uniforms, or full sleeved white shirts wearing badges and clipboards), and walk out of the exit. Cross the road lane - and another lane is clearly marked taxis. There's a long line of white taxis marked "Easy Cab" - these are aircon sedans, with meters.