One of the key ways to set up a winning hand is selecting the correct discard as the correct card can make be difference between making a point and a euchre. On an opponent's bid, choosing correct discard can go a long way towards setting them. With some hands, the choice is obvious (for example, holding five trump and an off suit nine, there is no question about what to discard). However most hands require more thought.
Many euchre players have a tendency to play the same way hand after hand. Here is where careful observation of your opponent's playing methods and habits can be helpful. Do they always lead their green suit? In other words, if hearts are trump do they lead clubs or spades, and if clubs are trump do they lead hearts or diamonds? If so, then given a choice, the best discard would be a singleton in the green suits, even if it's not your lowest ranked card. Discarding a singleton green king and holding a nine in next may set you up to trump the first trick. Saving an ace may be the only exception. There are also those players that tend to lead next (so if clubs were trump they would lead spades, and if hearts were trump they would lead diamonds). In these cases, discarding next would be the best choice, even if not the lowest ranked card (that is providing it's not an ace).
When at all possible you should first try to create a void in your hand. When playing with teams that you have never played before, you should try to create this void in a green suit. Most people tend to lead from a green suit rather than from next.
You should next consider which cards in your hand are most unlikely to take a trick (something like an off-suit nine). If there is a suit that you hold three of, discard the lowest of these. On hands where you have an ace-king (or an ace-king-X) combination in one suit, along with a king-X (or any X_X ) combination in another suit, hold the ace-king. You may be able to make both the ace and king good. Discard the smaller of a king-X (or X_X) set. With a little luck, you may be able to throw off one of these allowing you to avoid latter in the hand. Hopefully, you will then be able to make good use of a trump in this newly created void.
While rare, there are times it is the correct and perfectly legal move to discard the card that you picked up. An example would be holding five higher trump and picking up a nine.`
When making a lone call and having to choose between holding two aces or keeping an ace-king combination, discarding the single ace tends to be the better choice. This limits the opponent's opportunities to trump or over trump a suit.
Choosing the correct discard when the opposing team is playing alone is even more critical. In particular, a lone called from third seat requires a discard of a singleton next. As the dealer, that would include a singleton ace in next.
When having to choose between discarding an off suit ace and trump, always save the trump.
So far we have been talking about discarding as the dealer. There are other times during the game when discarding comes into play. While technically not a discard, cards thrown off during game play, are used an opportunity to give your partner information. We cover this in more detail in our section on 'communicating with your partner'.