If possible, you can register about ten minutes late to avoid the really crazy play.
There are three rules for these mega freerolls while in the early stages.
1. Don't
bluff.
2. Don't slow play.
3. Play a tight range aggressively.
Once the crazies get knocked out, you should continue to play tight. You can set mine and maybe try some suited connectors, but be willing to fold a flop if you don't have a really good hand. You often need top two pair or better in a multi player pot.
Position matters. Pay attention to what the players on your left are calling with.
When half the field is gone, you can loosen up a bit in late position. By now, you should have a feel for the other players at your table.
bluffing still rarely works past the flop, unless you are willing to go big all three streets. Three betting becomes an effective tool.
At the bubble stage, selectively raise preflop and 3bet shove mid stacks. Watch out for small stacks, because they have little to lose by calling. Watch out for stacks bigger than yours, because they can put your tournament to risk.
For the most part, stick to tight aggressive poker throughout freerolls. When you get under 15BB, shove really good hands and fold everything else.