I just read a few of the responses on here and have to make a comment of my own, cuz I feel I see some large blunders. If you're hit 2pr. headsup on a 2-fl brd. on the flop, you NEED to bet LARGE on the flop (not 1/2pot,.. 1/2 pot just prices the guy in, and if you're lucky, he'll reraise you with a fl.dr. & overs, a shove and it's a race,.. but maybe he's got trips?). Bet a minimum of 'pot' on the flop, or overbet the pot, say 1.5xpot, you want your opponent to be making MISTAKE to call your bet. If he calls and hits his flush,... too bad. But you always want to try to have him making a mistake if he were to call your bet (if he's on a fl. dr. without overs to the board, it'll be a huge mistake for him to call here).
Flop 2pr. on a 2-fl board, bet it hard! It also is dependant upon your table image and style of play. I'm only suggesting strategy here, taking into account that you're a TAG style player (similiar to what would be written in a poker book by a pro, as there strategy is based largely upon TAG style). If you've been playing weak/passive poker, the bet may also be good, as they'll be expecting you to check your strong hands. I suppose you could play it safe, let them hit or miss their potential draw here.. but how will you even know if they're on the draw if you don't come out betting? If you're playing TAG style poker, you will be more apt to get paid off and will win more pots. In this case, the flopped 2pr. on a 2-fl brd. warrants a big bet by you... bigger than the pot.