[bilbo-san]

Hand 1: I would wait for the turn to raise. Protect your hand.
Hand 2: Why check the turn? You've no reason to believe that your hand is no longer good. Bet the turn. If opponents are on draws, they will only pay you off now. If they have a straight, you'd rather find out now (the way you played it it's still not clear if the opponent wanted to C/R the turn or is just going crazy because he hit two pair and you showed weakness on the turn; you're behaviour either won you a lot of bets because you got lucky and he hit 2pair with Kx (but will usually just cost you 1BB when he doesn't hit it) OR it cost you a lot of bets because you overplayed vs. a straight).

Hand 3: I'd check-raise the flop. If villain does not have a piece of this, he won't call a turn raise, so I'll cash in now. If he's ahead of us, I'd also rather find out now. Oh, and only check if you are sure that villain will bet. Some people play AK or JJ or some such hand very passively here and will check behind on the flop, which would suck for you.

Hand 4: I fold this preflop -- I don't like T9o except perhaps on the button because flopping 2 pair isn't very great (straight draws), a T is very vulnerable to kicker problems (JTo, QTo and KTo are all marginal hands that lots of LP players consider premium hands and love to play) and you can't flop a flush draw. That said, check/fold the flop. Turn is fine (assuming no one else would have bet the flop if you had checked). The river call is very read-dependant, but if it is -EV, it's probably not by much.