Schnapsen is played with a 20-card French- or German-suited pack. Austrian Schnapsen packs come with 24 cards, as for Sechsundsechzig; you should strip out the Nines before playing. To play with a standard 52-card international pack (here US), remove the cards from Two to Nine inclusive.
The ranks and values of the cards, from high to low, follow the usual Central European model:
A, 10, K, Q, J
Determine the dealer by any acceptable means; thereafter, the deal alternates between the players. After the shuffle and cut, deal a batch of three cards to each player. The next card is placed face up on the table to determine the trump suit. Then another batch of two cards is dealt to each player, so that the players have five cards each. Finally the remaining undealt cards are stacked face down crosswise on top of the trump, so that the value of the trump card can still be seen. These ten cards form the talon, from which the players draw after each trick.
Non-dealer leads to the first trick. In the first part of the hand, a trick is taken by the highest card of the suit led, or by the highest trump if any is played. There is no obligation to follow suit or to trump. The trick is taken by the winner, who will count the point value of the two cards in the trick, as per the table above, towards the total of 66 needed to win the hand. After the trick is played, the winner of the trick takes the top card of the talon to replenish her hand, after which the loser does the same. The winner of the trick leads to the next.
In informal ("soft") games, it is legal for a player to look through the cards in the tricks that she has taken. However, when a trick is won by an opponent, you are only allowed to see it until the first card is played to the next trick.
The Trump Jack
As in many Central European Ace-Ten games, the holder of the lowest trump card (in this case the Jack) may exchange it for the trump turn-up. This can only be done by the player whose turn it is to lead, just before he leads to the trick. The exchange does not have to be made at the first possible opportunity - the holder of the trump jack can wait and exchange after any trick that he wins, as long as cards still remain in the talon, and the talon has not been closed. Once the talon has been closed or exhausted, the trump jack cannot be exchanged.
Marriages / Pairs
A "marriage" or "pair" (the matched King and Queen, or King and Ober, of any suit) may be melded at the start of any trick by the player whose turn it is to lead. This scores 20 points (for a plain marriage) or 40 points (for a royal marriage, i.e., a marriage in trumps). The player declares "20" or "40" and must lead one of the two cards to the trick and show the other card. Although a marriage can be melded any time that a player has the lead, the score does not count until the melder has taken a trick. So for example, a player may declare 40 for the King-Queen of trumps on the opening lead, but if she doesn't take a trick by the end of the hand her score is zero.
Exhausting the Talon
If no one closes, eventually the last two cards of the talon are drawn - the last face-down card goes to the winner of this trick and the face-up trump to the loser. After this the rules of play change and become more strict. Players must follow suit; also, subject to the requirement to follow suit the second player must beat the led card if possible. This means that if your opponent leads a non-trump:
you must play a higher card of the same suit if you can;
failing this you must play a lower card of the same suit;
if you have no card of the suit that was led you must play a trump;
if you have no trumps either you may play anything.
If your opponent leads a trump:
you must play a higher trump if possible;
if you have no higher trump you must play a lower trump;
if you have no trumps at all you may play anything.
At any point, when it is her turn to lead, either player may close the talon, by flipping over the trump turn-up and placing it face-down on the top of the talon. This is an undertaking to reach at least 66 card points using only the cards in one's hand. After the talon is closed, no more cards can be drawn from it, and the remaining cards are played according to the same rules as when the talon is exhausted: follow suit and head the trick if possible, otherwise trump.
The talon can only be closed after drawing a replacement card, when the players have hands of five cards each.
Note that in Schnapsen, unlike the German game 66, it is still possible to meld a marriage when leading to a trick, even after the talon has been closed. Therefore a non-dealer who is dealt the Ace, King and Queen of trumps can do the following: close the talon, lead the Ace, then declare 40 and lead the King followed by the Queen. The opponent cannot have more than one trump (one is in the talon), so this will win unless the opponent is able to put fewer than 8 card points on these three tricks, and then win the remaining two tricks.
A player who believes she has 66 or more points can declare this fact, claiming to have won the hand. Play ceases immediately. A claim may be made just after winning a trick or just after declaring a marriage, but not at any other time.
At this point there are two possibilities: the player claiming to be out is right, or she is wrong. If she is right, she scores points toward game as follows:
one game point, if the opponent has made at least 33 points;
two game points, if the opponent has made fewer than 33 points, but has won at least one trick (opponent is said to be Schneider);
three game points, if the opponent has won no tricks (opponent is said to be Schwarz).
If she is wrong, the opponent scores 2 game points, or 3 game points if the false claim is made before the opponent has taken a trick.
When a player closes the talon, reaches 66 points and goes out, the score is based on the tricks and points that the opponent had at the moment when the talon was closed: 1 game point if the opponent had 33 or more card points, 2 if the opponent had at least one trick but fewer than 33 points, and 3 if the talon was closed before the opponent won a trick. (This method of scoring is called Viennese closing (Wienerisch Zudrehen) or dark closing (Zudrehen finster).)
If a player closes and subsequently fails to reach 66 and go out, the penalty is 2 points to the opponent, or 3 if the opponent had no tricks when the talon was closed. These scores apply however few card points the opponent has taken. Note that it is not possible to go out after losing a trick. Therefore, if a player closes and plays on to the last card, but loses the last trick, his opponent automatically wins because the closing player cannot go out at this point, even if it turns out that he actually had 66 or more points.
The same scores of 2 or 3 game points apply in the unusual case where the opponent of the player who closed reaches 66 and wins by claiming first, before the closing player has gone out.
If neither player closed the talon and neither went out, i.e., play continued to the very last trick with the talon exhausted, the player who takes the last trick wins the hand, scoring one game point, irrespective of the number of card points the players have taken.
To determine the correctness of a claim, both players' points are counted up by going through the cards won in tricks and adding 20's and 40's for declared marriages, though if both players agree on each other's scores this step can be skipped. (It's no insult to ask for the points to be counted.)
When settling a claim, it may sometimes turn out that the player who did not claim actually had 66 or more points. This does not affect the score - so long as the claim was correct, the claiming player wins, however many points the opponent had. The opponent should have kept better track of the score and claimed earlier.
Both players start with 7 game points, and subtract the game points they win. The overall winner is the first player whose score reaches or passes zero.