It's not a great deal of help, but patience and luck are really what these are all about, particularly the ones with 2700 players and a $100 prize pool.
freerolls like the one CardsChat runs every week are a much better bet, they typically have a much flatter prize structure and give you a better chance of stringing together the couple of bucks you need to start a real
bankroll.
The other option is the country-specific freerolls that Full Tilt runs. I can only speak for the Australian ones, which had a lot of sitouts last time I played them, and usually only 1000 or so players. Not much of an edge in absolute terms, but it's a quantum leap above the standard games.
If you live in the US though, I imagine the US freeroll is probably not much different to the standard ones.
Good luck!