To crochet balls, you can follow these instructions^{wikihow.com 1 2}:

1. Make a slip knot and chain two stitches.
2. Work in six single crochets.
3. Make two single crochets in each previous stitch.
4. Alternate between two and one single crochets.
5. Complete three rounds of single crochets.
6. Single crochet decrease during the next round.
7. Stuff the ball.
8. Decrease again.

Alternatively, you can start with 7 single crochets made into a magic ring, then increase by 7 half-double crochets in each round until you reach the circumference you require. Work rounds straight (half-double crochet in each stitch without any increases), then decrease rounds and finish^{craftsy.com 2}.