Terminal 1:

As soon as you've gone through customs, you'll be in a big 'hallway'... which contains the moneychangers etc.

Walk 50 yards to your right. There's a lift. Go up to the floor above (Arrivals). Step outside on to the pavement.... walk to your right.
Stand on the kerb edge and flag in a white taxi that has just dropped off a passenger. Ask if they are using the meter. If they try to negotiate price, say no... meter only. If they won't agree to that...next please.
Rare I fail on the first one.

Ignore all touts !

You shouldn't really need to pay more than 2--300 pesos to anywhere within 3 miles of the airport terminals.