How to avoid pms?

Prevention. Try to stay hydrated and eat foods low in sodium to prevent bloating associated with pms. You could also eat foods that are rich in vitamin b6 (bananas and nuts) which helps to modulate hormones related to pms. Finally, exercise and stay active. Endorphins are released during physical activity which can also help relieve your symptoms when you do experience pms.
PMS. I agree, but also would suggest omega 3 fatty acids such as fish or flax seed oil taken daily as a supplement. If none of the simple things work then please see your doctor because we have many medical options to help, including hormonal manipulations as well as antidepressants-- used as needed rather than daily as for treatment of depression. You do not need to be miserable.