The first card thrown establishes the suit for that hand. Other players must play a card in this suit, if possible. Otherwise, they may play any card they wish*. The strongest card in the established suit will win the hand. Whichever player played that card collects that hand, turns it over and plays the first card in the next hand. Once a hand is complete, no one at the table may look at it. (this rule can be relaxed as much as desired, depending on amity, drunkenness, etc. However, all players should agree on the interpretation to be used, to avoid conflict.)
Within each suit, the Ace is the strongest card and the 6 is the weakest card. From strongest to weakest, the cards are:
Normal suit: Ace, King, Queen, Jack, 10, 9, 8, 7, 6.