Score the most points by calling exactly how many tricks you'll win each round — no more, no less.
Rounds
A game is a series of rounds. The first round deals the most cards; each round after deals one fewer, down to a final round of just 1 card.
Calling (bidding)
Looking at your hand, you call how many tricks you think you'll win that round. Everyone calls in turn. The running total of everyone's calls is shown as you go.
In rounds of 5+ cards, the last caller can't make the calls add up to exactly the number of cards — so at least one player is always forced to miss.
Trump
Most rounds have a trump suit, shown by a card flipped face-up. Trump cards beat every other suit. Some rounds (set by the host) are no-trump — highest card of the led suit simply wins.
Playing tricks
The highest caller leads the first trick and plays any card. Going round, everyone must follow the led suit if they can. If you have none of that suit, you may play anything — including a trump.
The trick is won by the highest trump played, or if no trump was played, the highest card of the suit that was led. Win a trick and you lead the next one.
Scoring
Hit your call exactly and you score (call × 2) + 10 — so calling and winning 3 is 16 points, and even calling 0 and winning 0 scores 10.
Miss your call and you score by how far off you were: out by 1 = 8, by 2 = 6, by 3 = 4, by 4 = 2, by 5 or more = 0.
Winning
After the final 1-card round, the highest total across all rounds wins.