I have tinted mine many times using two different methods.
First make sure you do it in the shade and have all of your tools laid out before startnig. You'll need a razor, a spray bottle with a soapy mixture (I use about an 1/8 cup of dishwashing detergent to a 1/2 gal of water), and a small squegee. You can usually pick up a window tinting squegee at your local auto parts store or Wal-mart.
Method 1.
It is very important that you get ANY gunk or dirt off of the window. You may want to lightly scrape the glass with a razor or very fine steel wool to make sure any dirt or buildup is gone. Clean the inside and outside of the window thoroughly with Glass Plus and newspaper.
Once you have the window clean, take the tint and lay it against the outside of the window with the clear backing facing outward and the tinted film facing inward. Take a razor and begin to slice the film following the edge of the window. Leave about an 1/2 inch extra on the bottom. This will get tucked into the rubber seal at the bottom of the window.
Once you have your tint trimmed, take your soapy solution and thoroughly soak the inside if the window where the tint will be applied. Then take a two pieces of masking tape and attached it to both sides of the film at one of the corners, then pull the tape apart to separate the film from the backing. After you have separated the film, take your soapy solution and thoroughly coat the sticky side of the tint.
Very carefully lift the tint from the top two edges and move to the inside and place the tint onto the window. Do your best to not crinkle the film, not touch anything but the window, including the film itself.
Take your soapy solution and thoroughly spray the film. This will allow you to slide the squegee on the film with runnnig the risk of scratching the film. (BTW, you can never spray enough soapy solution.) Then carefully insert the bottom of the film under the rubber seal using the squegee to push it and holding the rubber seal away from the window with your finger.
The previous step is a little tough but you may want to form a horizontal wave until you get the bottom where you want it under the seal. Then slide the film up to the correct position. Once you have the film in place, spray the film so more. Than take your squegee and start from the middle and start to squegee the soapy solution out from behind the film. Little by little work the larger bubbles to the outside of the window. ONne you have most of the major bubbles out, I usu. will walk away and work on something else (not another window, because you need to jump on the window you are working on in a seconds notice) for a few(10-15) minutes. Then go back to the window and spray some more solution and work the squegee again. Keep at it until all of the bubbles are out.
Don't roll the windows down for about 3 days. Then I will usu. roll them down a little and trim the top edge of the film just to make it follow the edge better.
The second method is pretty much the same , except that instead of laying the film on the windo to trim, I made a template out of poster board, then laid it on the film to trim. I like this way because it really makes for a clean trim.
Oh, and expect mistakes. I even still screw up a windows every now and then. But there's nothing better knowing that you did the tint job yourself. Good Luck! And let us know how it goes!