- Not leading trump to partner's call
- Leading trump on defense
- Turning down a bower when have 1 other trump
- Failing to call "next"
- Leading trump on fourth trick
- Passing with biddable hand
- Trumping partner's ace
- Leading right bower after calling "next"
- Not leading trump on own call
- Leading right bower against a loner
- Not leading "next" through third-hand loner
- Leading trump against a loner
- Forgetting that euchre is a partnership game
From information gathered at Yahoo's Euchre Science web site