Use a diffuser to blow-dry the hair. As the name implies, these attachments disperse the air as it blows onto the hair, leaving the curl undisturbed.
Don't use hot water to wash the hair, use warm water. Hot water tends to release whatever effect the perm has on the hair.
Don't use brushes, only wide-tooth combs.
If you want to comb permed hair, the time to do it is when you have conditioner in your hair. After that, towel-dry gently and leave it alone.
Permed hair is fragile and prone to breakage. Don't use rubber bands to tie the hair back or anything that has a tight grip and can pull hair out. Use bands covered in fabric if you want to pull it back.