Early stages you really want to only be employing a tight aggressive strategy where you only play few hands in order to build a stack early on. Phil hellmuth recommends you only play the top 10 hands in texas holdem in the early stages of an MTT. Although some may hate him, with 11 wsop bracelets, one can only infer that what he does is working.
Let's be clear - that recommendation of Top Ten hands by Hellmuth is targeted to absolute beginners. You will not see him EVER do that.
But yes, in the beginning you usually want to be tight AND very agressive (go for it when you do have it).
Understand that your strategy is dictated by stack sizes and blind structures. There are two different tourneys where I live to play. I have had success at both. Their structures dictate different styles.
Casino A - Starting stack is 2,000 and within 1 1/2 hours the blinds are 200-400. That means if you double your stack by then you still only have 10 BB. There is no room to play around and gamble in the beginning as it can cripple you. Tight is right. Shove or fold comes incredibly fast. I am more liable to fold SC, small PP out of position even in the early stages.
Casino B - Starting stack is 5,500 and within 1 1/2 hours the blinds are 200-400. That means if you double your stack by then you will have over 27 BB. There is some room to play around early. Spec hands in beginning are okay. I will set aside about 1500 to "gamble" with in early stages and play a little looser. I will definitely play SC, small PP from anywhere in the early stages (until my stack gets light). I have had both happen - chip up quickly and become table bully and also blow that 1500 and have to go uber tight. Both has gotten me to the money.
I will also count the number of participants, multiply that by starting stacks and divide by 10. That
tells me about how many chips I need to get to the final table. 40 players times 2,000 equals 80,000 divided by 10 is 8,000 chips. Now I know what I need to get to where I want to be for the ultimate goal. The blinds are my enemy (more than another player) and I adjust accordingly.
But yeah - get some books. Start with Phil Gordon's stuff then graduate to Harrington.