Well, I've been reading SSH, and while I've not had a chance to apply any of the great advice to my game, I found out in the first chapter that I'm a weak/tight player. If I'm this guy in MP with four folders, I'm not limping with any hand that beats you right now AND calling a raise with anything except maybe 77. I Can't put him on KK or even AK at this point. If I'm you, I'm betting 1/2 pot.
I don't think he has even TPGK right now because he (I) Probably would have made a bet for information/protection. Hands that seem very likely right are AJ, AT, A9, or midium pair (TT, 99, 88). given the way he plays, 77 is the only hand that cold beat you right now that imho, he could be playing. However, had I flopped trips, I may (have) checked/called as a trap to get you on the bigger rounds (This being NL, that doesn't really apply though

).
Any hand other then trips, (if I'm him) I'm check/folding...A 1/2 sized pot bet allows you to find out where he's at without risking a bunch of chips (see why I'm weak tight). Having said this, I think right now, you want him to fold. Any other move and he probably has you beat.
If he flat calls, and the turn is another high card, and he checks again, I'm checking the turn to see how he reacts on the river. If he bets out on the river, I think it's safe to assume he made his trips and a fold is called for. A w/t player can check/call to the river, but if he's first to act, he's not going to check the river, because he doesn't want to risk you not betting.