what to raise

[somethinlikeawar]

i've been questioning my pre-flop raises. what is 3x the blind if the big blind is 100? i would raise 300 on top of the 100 to make it 400 total?


i've especially been questioning raises head's up:
does it change head's up? for example, if i want to raise on the button do i raise more than if i'm not? (if i raise huge with an ace...aren't i going to think i may be up against something alot better and just be throwing my money away?)

that brings up the question of whether doubling the blind is acceptable. do i still raise the standard 3 or 4x the big blind?? do pro's double it head's up? (don't think i've ever seen pros double it)

also...do raises change during cash games? would doubling it at all times be more effective in a cash game, since people tend to make looser calls?


all input is appreciated. thanks!