You are South in this deal. It’s your turn to bid and your hand is not very strong. Should you bid or pass?
Your decisions during the auction should be influenced by what has happened so far. There are always clues there as to the strength of your opponents’ hands as well as your partner’s. Try and build up a picture of all four hands.
Mistake: Letting your opponents play at the 1-level
What is happening here? Both partner and East have passed. Even if West is quite strong, partner is marked with some points as East can have no more than five. It is quite likely that the points are relatively evenly divided.
The correct bid here is double. Partner won’t expect an opening hand as you have passed already. Don’t bid 1S as that will promise a 5-card suit. West will probably bid again but partner should be happy to compete with 2H.
The only time when you should pass at the 1-level is where you have lots of their trumps or you suspect that they have a safer place to play.
Principle: If possible do not let your opponents play at the 1-level.