Generally,.. very generally, bet around 3/4pot (but really it depends on so many factors, that it's not fair to say this). At it's most basic, a bet of 2/3 to 3/4 pot in live game, 3/4 to 7/8 in online game.
Some factors to consider:
position
how many are in the hand
who was the intial preflop raiser
playing styles of other players (are you heads up against a particularly aggressive player, who you'll know will be betting out on the flop with a cont. bet, whether he caught a piece of it or not)
are you heads up vs. a loose calling station, where you'll be able to value bet him on the next couple streets
what size is your chipstack in relation to others?
what size is your chipstack in relation to the blinds?
what stage of tourney are you in,.. or is it a cash game?
what is top pr. in this case?
what is the texture of the flop?
--- just a few variables to get ya started...... maybe pick up a book at the library,.. poker never has one 'right' way to play any hand,.. some are preferable over others but none are necessarily the 'right way'
Harrinton on Hold'em Vol.1 might get ya started (or maybe somethin' a bit more basic than that??)
Lucky you,.... lots to learn still,.....trust me,.. it never stops. If you're a player who thinks they know it all,... then you probably know very little. (this is the great thing about poker,.... it's infinite learning oppurtunities)