As Toby said, that's a good way.
I got in the habit of when I put screen protectors on, put it on with one hand, and flatten it out with a credit card edge with the other as I apply it, then you don't get room for air underneath. It's a little tricky, but after a few times, you become a pro. I just start at the top and apply it slowly while my other hand follows behind with a credit card making sure no air gets trapped underneath.