i had mine professionally done. it cost $180 out the door (including a banner of tint across the windshield). he took out my windows and everything (except the windshield, of course).
no bubbles. no flaws. nothing.
the fronts are 50% and the rears are 35%. i've seen people go 35% all the way around. but it's all out of personal preference (and state laws too :x ).
my suggestion; have a professional handle it. someone who stands by their work. if i did my tint, my car would never sink if submerged in water because of all the bubbles.