Effectively he is on the hijack here since there are only 5 players. QTo could maybe be considered a decent stealing hand in that spot, but it is still arguable whether to fold or not here, probably depends a lot on the table and opponents.
Not a bad flop for you, but it does hit your opp's range as well as yours, and there are draws on the board, flush and straight. You have to bet more on the flop 3/4 of the pot minimum, but closer to full pot would be better. If opp calls that, he most likely either has a strong draw or a made hand that is quite likely to beat you and that he is slowplaying (maybe a set of kings). If he raises you, you are most likely beat, unless he overplays a JT or Tx. As it turns out, he probably called you on the flop with nothing because your smallish bet was looking weak and he maybe thought this was just a continuation bet. Or he was just not thinking at all, not infrequent at the micros.
On the turn, you hit top two pairs, great. Note that at this stage your pair of T is worth nothing, except for the unlikely event that a T shows up on the river. But the Q also completes or improves straight draws and again hits the range of your opponent as well as yours (if he also has a Q, you now have a kicker problem: your kicker is only T, his might well be better than that if he has QJ or AQ). You HAVE to bet on the turn (and strongly consider folding if you are raised). By betting, you make your opponent pay to draw. You also bet for value against worse hands. 2/3rd to 3/4 of the pot or thereabouts would be about right I think, because you also want to keep control of the pot size with a hand that is good but could easily be beat on such a board. You also bet for information, because if you are raised you know you are beat. If you are just called, you also have to worry a lot whether you are against a slowplayed made hand or against a guy who can't let go of his draw (or against a draw that is so strong that the odds for calling are almost correct, such as a combo straight and flush draw).
Either way, any card on the river that completes a straight or flush draw (like a 9) should worry you big time. As played, you can check the river or try a small blocking bet. If you are raised or bet into, then you have to decide whether your opponent is bluffing or not. If the answer is no, then you are almost certainly beat and you should fold. If you think your opponent is bluffing because you showed weakness on the flop, turn and river, then you can call. But you should never have got in this situation to start with.
Position: you are "in position", or you "have position" when you act AFTER your opponent(s) on a given street. You are out of position when you act BEFORE them. In the case of this hand, you are out of position against your opponent.
You should read a few books about poker theory. Sklansky's No Limit Theory and Practice is very good. So is Professional No Limit. You should also read as many articles as you can on this site and on twoplustwo.com. There are very good articles explaining pot odds, bet sizing, drawing odds calculations, the importance of position, which hands to play in which position, etc.
Finally, when you post hands, you should not post the results (don't say what your opponent had or who won the hand), because this influences how people reply. You should also give reads on your opponent (how was he playing, what was your table image what were his stats), and you should for every street try to define a range of hands that your opponent is likely to have according to his actions. Read this: http://www.flopturnriver.com/phpBB2/...684e1c6a841bac