This really depends on what level surfer you are and where you live.
For beginners, it's best to surf at a patrolled beach when the surf isn't over your head.
For casual surfers, whatever the beach throws at you is usually OK, whenever you want to go out.
Pros travel everywhere and surf waves of all sizes.
If you live in a cold area, you'll need a wetsuit. If you live in a warm area, you only really need boardies, unless it gets cold in winter.