Very interesting question, especially considering the fact that, every time you enter a freeroll it is already a win in terms of EV
. Because in freerolls you cannot lose anything (except time spent), while you have always a chance to win something.
But if the question is, how to win freerolls consistently, then there are a lot of different factors to consider, as freerolls can be different from one another. For example, in some freerolls the best strategy is to play as tight as possible and wait till other players give you all the chips.
However, in some freeroll (usually with higher prizes) the players are playing more seriously, meaning that they won't give up the chips that easily, or even worse - there can be a lot of tough players in the field, that play solid poker. But even then, you still have a decent chance to succeed if you play a solid strategy.
Overall, since any freeroll is a tournament, there is a high variance. So you actually can't win all of them, no matter how bad or good your opponents are. That is why I usually play tight, and hope to get lucky more often then my opponents do))) so far this worked for me