There are two ways I have found that work for me, and one will get me endless ridicule. But that is OK 'cause I am happy to 'take one for the team' so you can all adjust your bottoms correctly....
The 'sit and leak' method (as I like to call it) really does not work because you never know how much air is in the cushion or how much you have let out. The biggest problem with Airhawks I think is overfilling them but no one seems to have a good method of adjusting them with any precision.... until now! Follow the simple step- by- step directions below and you too can reach heinie nirvana.
First of all, the easiest way to tell how much air is in the thing is to take the cushion out of the sleeve (easy), put it on a flat surface, blow it up until it is full and leave the stem open. The cushion will deflate until each cell is full but not pressurized. Now pick an amount of cells, I find half of them works great for me, and squeeze all the air out of them. In other words, leave 1/2 of the cells full of air and squeeze all the air out of the other half. I find using a hardcover book or cutting board or something helps in squeezing down the cells (no need to push, just get them more or less flat). Close the valve, replace the cushion and try it. Now if you want to adjust it for more or less air, just repeat all of the above but leave an extra cell or two full of air, or empty and extra cell or two. This way you can adjust it a bit at a time but mostly, you can repeat the way you fill the cushion in the future! That is the biggest problem I find- just how much air is in the cushion and how much more are you adding (or now much are you letting out)?
The second method is this: sit on the cushion, on the bike, just as you would ride it- feet on the pegs and all. Now, slide your hand under your butt and feel around for you sitz bones (the ishium), there is one on either side. It is pressure on the ishium that will cause major pain and in some cases serious medical conditions (seriously- Christopher Reeve). Feel how much air there seems to be between your ishium and the actual saddle: you want no more than 1/2" at least to start. While sitting on the bike you may be able to let a bit of air out of the cushion but you won't be able to blow any air into the cushion that you are sitting on- at least no one I know has been able to and I would pay good money to see that. The problem with this method (besides some people enjoy it so much they keep at it until they are arrested) is that it is tough to impossible to know how much you are adding / subtracting from the cushion. That is why I recommend the 'cell count' method outlined above.
By the way: you can use the cell count method to help someone else adjust his / her Airhawk but I have found that is not always the case with the 'find the ishium' method. I helped this one woman this one time and her husband seemed really put off- I have no idea why because the entire seat adjustment was a raging success IMO.
Best of luck with your seat and please feel free to post picture on any other forum on the internet.
Brian
Would the best approach be to fill it up and then sit on it and then let air out until you just barely touch seat? 
