|Jacks game pieces|
For the tennis version, it is basically a variation on the self-rally. Players toss the ball into the air, let it bounce, tap it up once with their racquet, then catch it in their non-racquet hand. This is a 'onesie'. Once this is accomplished, they repeat, tapping it up twice in a row for a 'twosie'. Continue with successively longer rallies. Player who can achieve the most 'ups' wins.
Play with a partner! You do the tap-ups, partner does the catching.
Adapted from USTA's Learn To Rally And Play booklet