[HTC Sensation] :
It all depends on how you install them. You have to be patient and take your time. Get a microfiber cloth and take your time.

The way I do a screen protector:

I do all my screen protectors in the bathroom (there's less dust in there cause it gets wet from steam in there from showers). Take your sensation and set it on something soft so it doesn't get scratched (don't use toilet paper as it has lots of small particles that come off of it).

Tip: Lay the protector over the screen before you start the process to see if there's overhang. If there's overhang, just even it so it's all the same around the whole screen. This will help you from having to much overhang after (cause you knew beforehand to even it out).

Get a small card (most screen protectors come with them, htc one doesn't). You can even use a mini credit card like the ones from bank of america. Whatever you use, use something with nice rounded edges.

Get a microfiber cloth and get it damp, not soaked, just damp ( I usually wash the cloth with soap and water then wring it out real good).

Now, open you screen protectors so you have one of them out and ready (don't peel it yet, just have it out). Take the microfiber and wipe the screen while it's laying flat, I normally go one way with it (like wipe it down). Keep doing this until there's no dust. Sometimes you can switch sides of the cloth so it's a fresh side. Eventually all the dust will be gone from the screen.

Take your small round card and the microfiber cloth and wrap the card with the cloth so the part that will rub the protector will be soft (it won't scratch it).

Now, take the screen protector and barely peel back the top (whole top, but not the whole protector). Now, position your top along the whole top of the phone and peel it down from underneath while you apply it the rest of the way. I take the card wrapped in microfiber and smooth it downwards while peeling the film with the other hand (tricky to do if you don't understand what I mean). This is the best way to avoid bubbles.

You're gonna have some small bubbles but if you have enough practice and experience (like me), you wont have any except the curved edges.

After the Procter is on,

Slowly squeegee the air bubbles on the flat part of the screen to the nearest edge with the card wrapped in microfiber. They will all come out, it just takes time. After the flat part of the screen has no more bubbles, work on the curved edges. The edges will take time, just do them slowly and kinda wrap the corner as you work out the bubbles. Do one corner at a time. Always push the bubbles out towards the edge, never go back and forth with the card.

After you have wrapped the corners and all the bubbles are out, they won't come back. They should be gone for good if you did it right and yours will look like mine.

Pro tip: If you do get dust, you can take the protector off and wash it very gently with liquid soap and water. Just rinse it off and shake the water off. It's ok to apply the protector a little bit wet (not soaked). The microfiber and card will absorb the little bit of water pushed out at the edges. If there's small residue after, don't worry, it goes away after a few days most of the time.

I hope this helps somebody as it's the best way I've found to do them. I've been doing screen protectors for years and think I have pretty much mastered it. I never get bubbles or dust anymore.

P.S. This process takes about 20 minutes, so don;t try to rush. You'll be happy you took the extra time and did it the right way after you're done using my method.

Good luck guys.