This is yet another very good drill to learn the importance of momentum.

a) Two players play and the point starts either with underhand feed or with serve
b) They play to 21 and scoring goes like this: if player A wins the first point, he gets 1 point. If player A then wins the second point in a row, he gets 2 points so his total score is 3. His next successive point is worth 3 points so the score is 6:0. If player B now wins the point he gets 1 point because that is his first successive point. If player A wins the next point he gets 1 point because his previous succession of 3 points was broke by player B.

Benefits:

• The players learn that the more successive points they win, the more they are worth. In real tennis the scoring is different but the emotional perception of the player is very similar. If one leads 5:1 and is caught by his opponent at 5:5, he feels as if he is losing. That's because successive points that you don't win make you feel very powerless. (At least that is true for most players.)
• Players also learn that they can get out of trouble faster. If one is behind 15:5 and he wins only 4 points in a row (1+2+3+4=10), he levels the score at 15:15. Again - in real tennis scoring doesn't go that way, but in player's minds it is very similar. If one leads 5:1 and the opponent gets to 5:3, most players become more tense and anxious.
• This is the way to approach playing from behind. Even though the gap seems too big, like at 5:1, if the trailing player can win two games in a row with many successive points, then the leading player will feel as if he is already losing. As you can imagine, playing from that mindset leads to poor results.