Collect sets of four by asking the other players.
Each player is dealt a hand of cards, usually five. On your turn, ask another player for a rank you already hold at least one card of. If they have cards of that rank they must hand them all over and you go again. If they do not, they say "go fish" and you draw from the deck, ending your turn. Whenever you collect all four cards of a rank you place them face up. The game ends when the deck and all hands are empty, and whoever collected the most sets wins.