Well, that's not exactly what I meant by steaming.
Here's how we generally accomplish it. This works especially well for back windows with defrosters. As long as the tint isn't in completely horrible shape, this will keep you from having to scrape anything. You can use a heat gun to do the heating, but caution will be required. It is easier to do it on a good and hot sunny day.
Things you'll need.
Regular Blue Windex
Straight Edged razor blade (To get the peeling started)
Trash bag or plastic large enough to cover the window you're peeling.
Paper Towels for final clean up.
Step 1
Spray the window down on the tint side with the blue Windex
Step 2
Cover the side you just sprayed with the plastic/bag
Step 3
Check to see that you've got everything covered and a layer of Windex trapped between the bag and the tint
Step 4
Close the car up and let it get good and hot. (10-15 min in the summer in the southern states)
Step 5
Start at an edge with the razor and carefully lift the edge, it should pull from the glass bringing all the glue and film with it. Spray some more Windex behind the tint as you work. If you get to a spot that feels like it is stuck. Stop, wet the window again, and let it heat back up. Don't keep pulling if it looks like the glue is still sticking. Cleaning glue off defrosters is a big pain to do right and not damage anything.
Step 6
Once the film and glue are off, double-check and clean up any spots that might have left glue behind. This is usually just a spot here and there around the edges and a paper towel and Windex will get it all.
Again, this is really what you want to use on windows with defrosters. Side windows that can be scraped, it is usually faster to just rip the film off, spray it down with Windex, and scrape the glue off with a straight razor blade. Granted, tint glue is nasty, snotty, sticky stuff when you get to scraping, so don't sling it all over the place. You can steam side windows, it's just usually a lot more work to do it.