Teaching kids the importance of good sportsmanship requires talking to them about their poor sportsmanship and explaining the idea of playing for fun. The next time the child gets upset after losing a game, calmly put the game away, and remove the child from the situation. Once she has had time to calm down, talk to her about why she felt upset. Help her to put words to her feelings while also praising other recent accomplishments.
Another tactic for a child that is a sore loser is to play a game that is about accomplishment rather than winning. For example, build a fort together, and focus on having fun and working together.
If the child has a habit of cheating to win, clearly set expectations at the beginning of the next game. Remind him that it is important to follow all the rules. Also, explain that winning and losing can be all luck in some games. If you notice him cheating while playing a game against friends, calmly take him aside, and ask him how he thinks the friends feel about him not playing fairly.
For a child who celebrates excessively, shift the conversation about the outcomes of games. Instead of asking whether she won, ask her whether she had fun. Compliment a specific skill she displayed during the game rather than the fact that she won.