What do you do when you hold middle pair and dont hit the flop?

[shadyridr]

This is probably the weakest part of my game as I never know what the right play is. Say I was dealt 9's and made a raise and got 2 callers. Now say the flop comes out 2-4-K. Here's where I'm stuck. Do I take a shot at the flop hoping nobody paired up or do I check/fold? The way I normally play it is I'll make a good raise on the flop and if I'm reraised I'll fold. But if I am called that's when I really get worried. If called what do I do on the turn? Or is making the raise just throwing my chips away?