I personally treat them like a regular tournament and try to play as best as I can, despite the maniacs. If you have time on your hands and play a lot of those, a good result is bound to come. Now, since it's a freeroll and you don't lose any of your money, if you want to go for an early double-up by shoving a relatively good hand, it's not a bad tactic. If you win you'll have a bigger stack for later on. If you lose just go for the next one. Personally I don't do this a lot unless I have Aces or Kings early on, but it's not a bad tactic for a freroll. Of course if there are already 3-4 people all in, you'd better think twice about it.
Bottom line, it's not much about playing poker, more about applying tournament strategies (playing your position, be aware of your stack in relation to the blinds, pick your spots etc.)