Basic rule of thumb for this film: You can't clean the adhesive side. You can maybe pick a piece of dust off of it by using a toothpick or some other hard, pointy thing, but this is almost impossible to do without making it worse.
I've gone through a ton of this stuff since the original iPhone came out, so I know pretty much the best way to install it. Here are some tips that will help:
1. Stretch out a white t-shirt on a kitchen counter. This is your work surface.
2. Get a credit card or debit card or some other piece of thick plastic with a straight edge on it. You will use this to apply the film to the phone.
3. Put on a baseball cap. This will help prevent hair, skin flakes, etc. from falling off of you and onto the film while you are applying it.
4. Clean your iPhone's screen thoroughly, with a soft lint-free cloth. If the screen isn't perfectly clean before you put the film on, it's not going to be clean after you put the film on, either. There should be no fingerprints and no dust on the phone's screen.
5. Orient the phone so that the home button is at your right, and the top of the phone at your left.
6. When you peel the protective backing off of the film, make sure the sticky side of the film stays DOWN. NEVER let it face upward; doing so guarantees that you will catch some dust. You may need to hold the film by pressing its edges (not its surfaces) between your fingers.
7. Carefully position the film on the TOP edge of the screen (on your left), so that the earpiece slit aligns correctly. Then, use the debit/credit card to push the film down the length of the phone. This will reduce the chance of air bubbles forming under the film. If you've done this correctly, the home button will properly align with the hole in the film.
One final piece of advice: The anti-glare film is much, much better than the crystal film at hiding marks.