The key to Spades is bidding wisely and working with your partner. Master these skills and you'll always be a dangerous opponent.
Bidding
A bid is an educated guess of how many tricks you think you will win. When thinking about your bid here are some good rules of thumb to get you started: First, every Ace in your hand is probably good for one trick. The only time this is not true is when an opponent is out of a suit at the very beginning of the game and can trump in immediately, but this is statistically rare. Second, a run of Spades from Ace down is good for the length of the run. For example, if you have Ace, King and Queen of Spades, then you are guaranteed at least three tricks.
Runs also apply to other suits, but with each lead of a suit the odds of someone being out, and therefore able to trump in, go up. An Ace and King in a suit is likely to be good for two tricks, but not necessarily. And an Ace, King, and Queen might work for three tricks, but don't count on it!
Additionally, if you can "outlast" the other players, you have additional guaranteed tricks. For example, if you have Ace, Queen and Five of Spades you can play your Ace for one trick, and when the King is played you can play your Five, leaving your Queen in your hand as the remaining high trump.
If the Sandbags rule is being used, it will effect the intelligent player's bidding. With no Sandbags, there is no penalty for taking more tricks than you bid. Because of this you should bid conservatively to insure you do not get negative points by being set. With Sandbags, the game is more interesting -- if you underbid you will accumulate Sandbags, which will eventually lead to minus100 points. If you overbid, you will take negative points for missing your bid. To succeed you must hit your bid consistently and that takes much more skill.
Nil & Double Nil
The Nil and Double Nil are a special type of bid in that you are hoping to earn a large amount of points by taking no tricks. In a Double Nil you can make more points, but you also must decide before you look at your cards!
If passing is allowed, you should always pass high cards, especially trump. The other cards to consider passing are those with suits of which you have fewest. If you can void yourself of a suit, then when that suit is led you can play the dangerous, non-Spade cards from your hand. The more cards you are allowed to pass on a Nil bid, the easier it is to make that bid. With three cards passed it is relatively easy to make a Nil bid.
A Double NIL is a large gamble and should only be used if your side is losing by a significant amount.
The Hand
In general, if you are trying to make your bid you should try to take tricks and once you have made your bid you should avoid them. Easy enough to say!
Remember that you have a teammate. If your partner is sure to win a trick, don't take it away without good reason (for example, if they are trying to make a nil bid).
When passing cards to your partner, remember what you passed as you can use that knowledge to play more intelligently as a team with your partner.
If you are sure that your partner is not going to make his bid, you should attempt to take extra tricks in order to cover for him -- but only do this under unusual circumstances. Your partner is bidding on their hand -- you should worry about your own bid and generally trust that your partner knows what he is doing.
Try to be aware of who is void of what suits, and how everyone is doing. If an opponent has bid Nil, it is much better to give them a trick even if it means risking your own bid, and it's always worth taking an extra trick or two to "Set" your opponents by keeping them from making their Bid.
Conclusions
When playing Spades it is important to always remember you have a partner. By paying close attention to what cards fall early in the game you can play to your partner's strength and they can play to yours. At its best, both you and your partner's hands will be stronger than they ever could be individually and this strength is both satisfying to grasp and the secret to success in the game of Spades.
(Written with the assistance of Joe Andrews, President of the American Hearts and Spades Players' Association.)
