It's always very difficult. I suck at it. Wasted the first one, the second one no bubbles but slightly off center, good enough.
Some tips I've picked up from watching pros put screen protectors on over the years:
- Wipe screen super well with alcohol. Wipes or a cloth that doesn't leave any dust or fibers
- The little dust or fiber particles is really what messes things up
- Once wiped, dab the screen entirely with a little piece of (not too sticky) tape. This will get rid of any remaining particles (hopefully). At this point, prepare some extra bits of tape you can easily pick up one handed
- Remove only partially the protective film on the screen protector in the longitudinal direction. Say a few centimeters.
- Align screen protector with the top of the screen
- It's important to note that from the moment you've wiped and cleaned the screen with tape, you should move quickly. Don't leave the screen just sitting there for more than a few seconds. There's always particles flying around.
- As you press down the top of the now partially attached screen protector, pull back slowly the protective film from underneath with one hand, while you slide down and press your other hand (previously pressing down the top) in one fluid motion
- There will be some bubbles. Hopefully it's just air and you can use a soft plastic card or something to push them out from center to the nearest side.
- If you see the bubble doesn't move easily and no matter what you do stays there and is small, gues what... it's a dust particle
- The only thing to do then requires some dexterity and the previously prepared tape. Attach one strip of tape to the corner closest to the particle. Lift the protector until the particle is exposed. Use a second part of tape to remove it from either the screen or the protector. Once removed, let the screen protector fall back into place.
- I've only ever successfully removed one particle, if there's many your probably screwed. I've never managed to reattach a screen protector that had the film removed...
Hope this helps some