So, I'll help too.
There are 2 basic airs you are looking at, booters and ollies.
In order to learn these, you first should learn to pop with both feet. As you come over a nice roller or approach a steep section of run, just pop both feet into the air, don't flex the board or press or do anything but give the natural flow of the jump a little 3-6 inch pop with your knees. This is the basic mechanic of leaving the lip of a proper booter, but as Donutz said, there are several other issues like speed, setup, etc.
The best way I can explain to ollie off a roller is to put some pressure towards your front foot as you approach, then right as you are ready to use that tail flex, you roll your weight a bit back as you initiate the ollie. You can ollie without this, but you can really boost it and get all the snap out of your board this way. Just remember that as you go into the air and land that you want to be center weighted.
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