First of all, I am not a professional tint installer. Now that that is out of the way, I will say that I've been doing my own tint since the 90's. Anyone can do this, it just takes a lot of practice. If you're patient and aren't afraid to take on a challenge you can do this.
Okay, here we go...
Tools needed are:
Razor, or utility knife blade (just the blade not the whole knife)
Soapy water in a spray bottle (any ammonia free soap will do)
Tape (scotch, masking, etc)
Plastic card (credit/debit, library, drivers licence, etc)
Assistant (not needed, but helpful) this was added to the tool list, at the suggestion of my wife......... my assistant
Tint (duh). I use automotive security film, from Concord solar control window films (aka Concord Window Films). They have many variations of film to chose from, I just chose to spend a little extra for the security film to protect my car/truck. A "standard" roll of film is still much better quality than the crap you can buy at the store. Prices vary depending on film type, color and size. I usually buy a 50' roll, and it lasts a long time. You can do a lot of windows with 50' of film (and it gives you plenty of extra to mess up and try again).
Now that you've got the supplies, it's time to get to work.
* Cut a piece of tint larger than the window you plan to tint. This doesn't have to be a lot bigger. Just enough to cover the window, and give you room to trim.
* Take the piece you cut and put 2 pieces of tape on a corner. 1 piece faces the other (so the sticky sides would touch if the tint wasn't in between). Make sure you fold the ends of the tape over, so they don't stick together where the tint isn't in between them. (see below pic)
* Pull the two pieces of tape away from each other. This will separate the actual tint, from the clear protective backing. Only peel back enough so that you can determine which side is the tint, and which side is the clear backing that is to be removed later.
* From outside the car, place the tint on the window you are working on, with the clear layer side facing out (when applied to the inside of the window that will put the "sticky" side of the tint against the glass). Helpful tip... Spray the outside of the window with your soapy water. For some reason even the non-adhesive side of the tint will hold onto the window when it's wet.
* Trim your tint a bit closer to the actual size of the window, but still leave a little room for trim. This mainly concerns extra length at the bottom of the window.
* Now set that aside for a moment, and....... VERY IMPORTANT.... clean the window that you are going to tint. Helpful tip... do not do all of them yet, just the one you are currently doing. While you are moving around, dust could stir up, and land on a window that was already cleaned. If you don't reclean that window you will get a white spot where you just tinted over dust. Most people just do all the windows at once, but I prefer to have good looking tint, instead of being lazy and/or rushing things.
* There are actually 2 steps to "cleaning" a window. Don't just wash it with windex. 1st, yes hit it with window clearer (or even soapy water, since you'll already have this on hand). But the second step that most people leave out is what causes the home jobs, to look worse than the professional jobs. Go over EVERY INCH of the window with a razor blade. This will scrape off any bits of stuff, struck to the window, that the window cleaner didn't pick up. Trust me there is more there than you think. The older the car, the worse it is.
Anyway, slide the razor across the window like you are shaving it. Helpful tip... Spray the window with the soapy water for this step so you can see where you "shaved", and because a little extra soap never hurts when trying to clean something.
* Repeat this step until the razor slides smoothly across the glass, and you don't see any dirt on the edge of the blade after you "shave".
* Now that the window is clean. Liberally spray the window with soapy water. Slowly peel the backing off the tint, while spraying it with soapy water too. Helpful tip... This is easier if you have a helper (wife, kid, buddy, whoever). They can peel while you spray and also hold one end so it doesn't curl back on itself.
* Place the tint on the window. The soapy water will let you slide the tint freely around the window, for a perfect fit. Slide about 3/8" of tint below/inside the rubber strip at the bottom of your window. You may need to use the plastic card for this depending on how tight it sits against the glass. This will prevent the tint from peeling up later, due to constantly being scraped every time you put the window down, and it would look like poo to have a line at the bottom of the windows.
* Use the plastic card to squeegee the soapy water out from under the tint. If you find a bubble, or pocket of water, just patiently work it out. IMPORTANT... Work from the center out. This works the water, and any air bubble out to the edges where they can escape.
* Once you've worked your way to the edge, use the razor to trim the tint to a smooth line. Helpful tip... You won't be able to smooth all the soapy water out, until you make this last trim, so don't worry if there are a few bubbles as you approach the edges.
* Now you are pretty much done with this window. Go over it as needed to smooth out any bubbles that may reform (they will do this near the edges for about 15 minutes. Just take your time and work them to the edge. Don't try to force them along, because this will crease the tint, which leaves a very ugly line. Patience is key. If you crease it you might as well peel it off and cut a new piece, because that one is done. There is no "fixing" a crease. You can work the bubbles out with the plastic card or squeegee but a crease will leave a very visible line regardless of how much you work it.
While I'm on the topic of creases, I'm going to back peddle a bit. You need to be careful when you're getting ready to apply the film to the window after peeling the backing. This is where the assistant is helpful. If you're peeling the backing off and it curls up and touches itself it's done, you'll need a new piece. It will either crease or leave an ugly spot where the adhesive contacted itself. Applying the soapy water as you peel the backing helps to keep the film from wanting to curl.
Repeat theses steps for all the windows.
* Let the windows dry for AT LEAST 3 days before rolling them down. My recommendation is to wait more like 4, or 5 days (depending on the weather), but 3 is bare minimum.
* Don't use any cleaner with amonia on your tint. The amonia will slowly damage it, leaving it that ugly purple faded color that you see on old cars with tint. If your wife, or kids decide to do you a favor and wash your car, don't freak out if they use something with amonia in it. A time here, or there won't hurt, but normal use will.
*Now for the really hard part. There are two methods for the back window of a car since they tend to be bowl shaped rather than only curved in one direction. You can either splice smaller more manageable pieces or shrink fit it.
If you chose to splice pieces together, start like you normally would. At the seam, you want to overlap the two pieces of tint by about 1" or so. Then half way through the double thick layer, make a cut with your razor. Remove the two newly created 0.5" pieces, and smooth out the tint as normal (see below pic). If done right, this seam should be nearly invisible from the inside, and completely invisible from the outside. It's tough to do, but depending on how much curve the rear window has (each car/truck is different) it can be easier than working one large piece. Here's a sketch of the technique.
The second method is how the shops do it, and takes more time, and the addition of 1 more tool. That tool is a low setting heat gun, or hair dryer. Something to apply heat to the film to shrink fit it to the window.
*Start just like you do the doors. Start by laying the film on the outside of the glass, and holding it in place with the soapy water.
*Now squeegee the film to the window as if you were leaving it there (DON'T peel the backing yet), starting from the center and working toward the edges.
*As you start working away from center, you'll notice the compound radius of the window will create gaps where the tint contacts the glass. Don't fold these down and create a crease. A crease is forever, and will look like crap so be patient and avoid creasing it.
*Instead slowly work them away from center with the squeegee, and gentle heat (I don't recommend a heat gun, but it technically will work if you are good enough with one). Much like creases, melting the film is permanent, and will look like crap, so keep the heat mild.
*Trim the excess material (along the outer edges) away so it more closely matches the window's shape.
*Go back and keep slowly working the wrinkles away from center, and using the heat to "stretch" the film to match the contour of the glass. You'll need to make a lot of passes before it's smooth.
*Again trim the excess film. You'll need to repeat the smooth/trim process multiple times. The final trim will be done when the film is much smooth to the glass.
*Once everything is smooth and looks good take the tint off the car and relocate to the inside.
*Spray the soapy water on the inside of the window now. (I also clean the outside again, prior to this so I can clearly see areas in the film that need worked)
*Slowly remove the backing, and apply the film to the window, avoiding touching the tint to any of the cloth or dirty surfaces in the car.
*The film should be pretty smooth if your previous prep was done right, but will still need a little squeegeeing to get the excess water out, and assure there are no bubbles.
*If you do have a bubble or two you should be able to work these out like the side windows. No heat should be needed from this side of the car.
Don't try to tint your windows thinking it will be easy, or that you'll get it right the first time you try it. It takes practice so be sure to buy extra film. Having been tinting windows for as long as I have, I still occasionally need to peel a piece and try again. Yes the first car you do will be very frustrating, and may cost as much in material to have had it professionally done. However every time you do it you'll get a little better. After a while you'll be able to do all your own cars/trucks and save a fortune doing it. My $80 roll of security film was enough to do multiple cars. I did my Charger, Ram and a still have a bunch left. 15-20 years ago I wasn't able to do it so cheap, but you've got to start somewhere.
Good luck. Just take your time, and with practice you'll be a pro in no time.