From the campaign:
Playing Pairs is easy. The most important rule is that points are bad. Also, there is no winner, just one loser: the first player who scores too many points. For example, In a 4-player game, the loser is the first player to collect 16 points.
To begin each round, the dealer gives a card to each player. The low card goes first, and play passes to the left. On your turn, you may take a card or fold. If you take a card and catch a pair (any two cards of the same rank), the hand ends, and you score the value of that card. For example, if you got a pair of 8's, you score 8 points. If you don't get a pair, you're safe, and play moves to the left.
If you fold, you score the lowest card in play, and the hand ends. So if there is a 2 on the table, you could fold for 2 points rather than risking pairing your 8. Set your scoring cards aside, discard the rest, and play another hand, until someone goes out.