Early on in those big tournaments I find there is always at least 1 or 2 big donkeys at your table, find out who they are fast and you can play some weaker hands against them. They will be bluffing deep into hands early on in the tournament. And it's a good idea to play hands with implied odds
against anyone early on especially in multiway pots. But generally play less hands early on than later in the tournament. And keep in mind if you play a big one with over 800 people, it's very unlikely you'll go deep you'll need to win races. The chances of winning or cashing in a 6 handed sng are much much higher.