You are declarer and you have a two-way finesse to take. Eg. A J 2 opposite K 10 3. Ideally you would like the opponents to lead the suit for you and guarantee you three tricks. Unfortunately, it is not possible to arrange an endplay and you will have to make a decision.
Failing all else you should choose the opponent you would least like to win the trick and finesse through them. To sum it up “FINESSE THROUGH GRUMPY”