Step 1: When to air kiss
Don't use it on friends and people you actually like; you can kiss and hug them the traditional way. Where air kissing comes in useful is when dealing with people for whom you have no real affection, but who still need greeting anyway.
Step 2: The greeting
Make it clear you are going for an air kiss by loudly exclaiming the person's name beforehand - as if you are thrilled to see them and want everyone to know it. If you can't remember, or don't know their name, then crying out "Darling" or "Honey" will do just as well.
Step 3: Lean in
Turn your head 45 degrees and lean in towards them, cheek thrust forwards. They will do the same, making you cheek to cheek. Some air kissers actually gently touch cheeks, but this is a bad idea. It can lead to stubble burn, or worse- you might blend foundations, creating potentially awful make-up colour-schemes.
Step 4: The kiss
Purse your lips together and kiss the air just to the side of their face. Then switch sides and repeat. Always go for at least two kisses. One is lazy and makes you look like an amateur. If you really want to show you are a high roller, go for three or four. They will think it's a habit you picked up in LA and be suitably impressed.
Step 5: Sound
A discreet kiss sound is cute and may actually get the recipient thinking you like them. But for maximum effect go for a loud "MWAH". This lets anyone nearby know you are air kissing, just in case they weren't sure.
Step 6: Hands
You can embellish the kiss by grasping each other's hands at chest height. This looks friendly, but actually acts as a barrier, enabling you to fend them off if they get too close.
Step 7: Retaliation
If you really want to annoy an air kisser, plant a big smacker right on the cheek. This blatant disregard for the rules will send them into a tailspin, so you can make your excuses and leave.