If your doing it yourself make sure you thouroughly clean the glass
with a used(almost worn out)scouring pad,the one with the sponge
on the other side
When applying film make sure the glass is always wet with soapy water
Have you got the plastic tool to squeeze the water out with?
Always start from the middle and push outwards.
Oh and you need a seriously sharp surgical knife(thats for your wrists)
coz if you dont do it properly its quicker to slash your wrists,and have red tints