How often do we know when to lead a trump verses a suit lead? If we listen to the bidding we may get a clue. Everything depends on various situations.
1. Do we hold all the remaining high card points?
2. Do the opponents have a fit?
3. When the opponents have bid three or four suits and wind up playing in one of them.
4. When partner has doubled the opponents' part-score contract for penalty. Low-level penalty doubles usually indicate a big trump stack and it is therefore very attractive, if not mandatory, to lead a trump.
Let us look at the following hands to help you make these decisions.