Wait in the place that people going to the airport are left off by taxis.
You will find that this tactic will not work at most airports. Taxis usually have to be authorized to pick up from the airport and even pay fees for the privilege of doing so. If an unauthorized taxi is found to pick up passengers from the drop off zone, they could be in serious trouble.
Even if the driver would be authorized to make airport pick ups, if they just arrived to drop off another passengers, they would most likely point you to the taxi pick up point where their colleagues have been waiting in line. Again, if they are found to skip that line by picking up in the drop off zone, they could face serious trouble.
I've never been ripped off when doing this.
Probably because you didn't do it too often if at all.