I don't have experience applying one myself, but watching the installers at the mall cover mine for me, I can tell you to be sure that the device is completely powered off before applying the spray solution, and don't turn it on for a couple hours after application is done, per their instructions.
Also, be very patient and understand that you'll have to squeegee the hell out of that thing for what seems like ages before it looks decent. Keep the squeegee moist so you don't scratch the film, and keep in mind that if it looks a little rough the day of application, it does take about 48 hours to fully bond to the surface of the iPad, so don't be too hasty in deciding that it looks like crap. A lot of minor imperfections/bubbles will correct themselves, but do be as thorough as possible.
Best of luck to you.