I definitely agree that the only way to go in freerolls is to play tight, tight, tight. It's hard to do sometimes because they can be long and one can get pretty impatient, but it's almost always better to wait for good cards and play them aggressively.
Suited connectors are nice for limping too, because you can flop a monster hand and get paid off nicely. Otherwise, best to fold. Even if you have a solid hand (say, KT or KJ), someone is likely to have something better; if they don't, with all the other callers someone will outdraw you anyway!