Start with 8 chain stitches

Connect them to create a loop,using 1 slip stitch

Then just go round and round in this pattern:
1# round 2 single crochets all the
way around
2# round 1,1,1,2 single crochets
3# round 1,1,1,1,2 single crochets
...
20# round 1 single crochet all the
way around

Then crochet as in the 20th round until beret is the depth you want it to be

Decrease the number of stitches by skipping stitch 3,then stitch 2 in the next round

Enjoy :)