I've been trying to figure that out. Past three weeks I started to play very seriously these freerolls as I'm trying to build something out of zero. It's been really tough for me as I finish on the money at about just 20% of the time against total donks. I usually play solid until I make that big mistake and turn myself short stacked.
Four things I started to figure out, I'd be glad if someone pointed out some flaws in my personal observations:
1 - Pots get out of control before the flop VERY often. Happens because a lot of people raise from early position with medium-strenght hands like QJ, any KT+, suited ace-rag, and a lot of people calls. Which means that if you decide to play a lot of hands, your stack is very likely to shrink and expand a lot. You are looking for very strong situations to play flops. Luckily for you, your opposition is very likely to commit mistakes that will lead you to a double up as long as you hit a strong flop. Induce a shove pre-flop with AA and KK, raise with QQ and AK, never 3-bet with AQ or any pocket pair below QQ. You are looking for set mining/overpair situations with JJ or worse. Hands like suited connectors, ace-rag suited and broadways, you shouldn't really play outside of the blinds/button/cutoff.
2 - There's very little fold equity post flop. You will see a lot of multiways pot and is highly unlikely that someone won't hit a piece of the flop. They'll chase the showdown on draws, ace high and with medium-bottom pair. So don't try fancy plays like floats, semi-bluffs or double/triple barrell bluffs. The only situations that you'll have bluffing or semi-bluffing opportunities, is when it's pretty clear someone missed their draws.
3 - Exercise a lot of pot control post-flop, but try not to fold a good pair or two pair on a dry board. Specially when your opponent is covered by you. I guarantee if you play tight with your hand selection and somehow keep you'll win most of the showdowns, even with weak holdings like top pair or bottom two pair. I tend to check behind a lot of turns and rivers that I know I should bet, but I know that I would eventually get pot committed on a later street if I bet.
4 - When you flop sets in multiway pots, you will get three streets of value. Luckily for you, they don't know it's way more likely for you to draw a full house while on a set, than it's for them to draw a gutshot straight or hit an ace to go along with his middle pair. Set mining is the key here. Most of your double-triple ups are coming either from hitting a set on the flop, pre flop action with aces or kings, or hitting hard a board from blinds or co/button.
5 - Take notes. Avoid making big decisions against someone you don't have any notes. There'll be a lot of showdons. Note who is calling anything with a draw, someone's shoving range - is he shoving 77 pre flop? AJ? calling range post flop, etc.