Commit Often
Commit small amounts of code and do it frequently.
Rationale
Keeping code on your local machine for more than a day can lead to problems when you come to check in. If you make large changes, then resolving the merge with everyone else that has checked in can cause problems.
Ideally committing small changes, and doing it frequently gives you the benefit of integration with others often. But also gives the ability to revert back a step, which is especially useful when refactoring code.