When should you branch?

Question

When working with a SCM system, when should you branch?

Answer 1

Whenever you feel like it.

You probably won't very frequently if you work with a centralized SCM since the branches are part of the official repository, and that doesn't really invite much experimentation, not to mention that merges really hurt.

OTOH, there's no technical difference between a branch and a checkout in distributed SCMs, and merges are a lot easier. You'll feel like branching a whole lot more often.