All Folded to the Small Blind

I am curious about the proper strategy in both ring games and tourneys. If you are in the small blind and the table folds around to you what is the correct play if you have a big hand versus a marginal hand versus a crap hand? I realize that the situation can depend on the calling habits of the person in the big blind etc. I am just wondering if there is a "best" strategy in these situations.

Thanks.

NWF, covered it.