In the two-player game of Go Fish, using a standard desk of 52 cards, where a set consists of all four cards of a given rank, is there a known optimal strategy?
When I play, if I can ask for a rank that I know the other player has, then I'll ask for it; but if not, I'll ask for the rank that I have asked for least-recently, on the grounds that my opponent has had most time to pick up that rank.
However, it might be better to bias the choice towards ranks I already have three or two cards of.