Needless to to say but if an opponents exposed cards beats your whole hand, it is best to fold.
Also look at all the players exposed cards, remember this game is played with a single deck so if you see a lot of cards which you would need to complete a hand it makes it less likely you will be dealt them.
Remember that in 7 card stud poker the antes can vary a lot depending on where you're playing. Basically the higher the % players are required to put up the more aggressive a player should be (to steal the antes).
In 7 Card Stud, fifth street is a decision time, as the betting limit increases, this is the time to fold a poor hand, especially against aggressive betting. If you stay in be sure you can play your hand out to the end.