Of all the positions to be stealing from in an MTT, middle position can often be the most effective, simply because it's not as predictable a stealing position as late position. As such, middle position is where you can really start playing some marginal hands.
At the right kind of table, open-raising a wide range from middle position can be a profitable play. This will, of course, depend on the players at your table. If you are facing an opponent who never folds his big blind, stealing is not the best course of action (but playing good hands is!). However, if you have players at your table who don't like playing hands out of position and are not aggressively defending their big blinds, it can be the perfect time to pick up pots when you are card-dead.
Positional defenders
One thing to look out for though is what I like to call positional defenders. These are players who don’t necessarily defend their blinds, but instead tend to defend their cut-off or button. They call or re-raise from the cut-off and button, both to prevent the blinds from joining in on the action and to isolate you, knowing they will have position post-flop –the good thing is these players are pretty easy to identify. If you see a player calling raises or making re-raises frequently from late position, you’ve found a positional defender. This doesn't mean you have to stop raising first to act if there is one at your table; you just need to adjust your game to account for it.
In fact, there are a lot of chips to be gained from positional defenders if you play them right, because they won't be able to help themselves and will insist on making a play at the pot. If you open-raise and a positional defender calls and you hit the flop, be aggressive on the flop. If they raise, you can win a big pot. If they call, don't be afraid to check on the turn, because positional defenders love nothing more than floating on the flop in order to take a stab on the turn if you show you did not like their flop call.
In a typical situation, you should be raising most pairs and Broadway cards if you’re first into the pot in middle position. It’s also recommended to increase the frequency of raising with non-standard hands like suited connectors and suited Aces and Kings to keep your opponents off balance. You must of course evaluate the remaining players in the hand and their stack sizes and tendencies, but your range really should be wider here than when you are in early position.