First and foremost, if I were you, I would work on my short stack play. There is *a lot* more to it than just pushing with decent cards. You have to take your position, other players and many other things into consideration. To be honest, I would say work on this first as it is most likely one of the most important things to learn in MTT play.

As far as building a stack goes... That is a good question and if I knew the whole answer I would be making it a lot further than the top 20%(on a regular basis). This is where a mix of skill and luck(don't like that word) comes in. You can't do much without cards that hit a flop.

However, if you have a good read on your opponents you can play odd hands in position and try to flop a monster or at least out flop them. An example could be: Say you have a tight player that only seems to raise with hands like AK, AQ etc. You can call here, assuming your stack wont be too damaged by a call, and if the flop pairs you and misses them, you stand a real chance of taking the pot and maybe a large portion of the other guy's chips. This type of play serves two purposes. The first is the obvious one... you build you stack..lol The second is that if the other players see you call with a junk hand and win against big hands they are more likely to call your raises or reraise you with marginal hands.