check-minraising the flop should send off signals to him, and unless he's retarded he's probably slowing down. i'm usually always leading this out. if he has some sort of hand he's at least calling you, and if he has a big pair or an AK type hand, he's probably raising you. you lose a lot of money by checking here IMO.

a line i like is leading out, and when he raises smooth call his raise then check the turn. this is a fairly common line i see with weak hands, and almost always you'll get him to fire another barrel if you check to him on the turn.