Finding the Queen
When declarer is missing the queen in a suit, there are many techniques to use before resorting to a 50-50 finesse.
If there is only one way to finesse, such as:KJ2 opposite A76 or A765 opposite KJ43, the old adage applies:
"Eight Ever, Nine Never." This means that with 8 (or fewer) cards in the suit, always (ever) finesse. With 9 (or more) cards in the suit,
...