Check Diffs Before Commit

Before committing changes to the version control system, read through a diff of what you've changed. This helps you:

Help the current codebase monotonically improve
Make sure you only changed what you meant to change and didn't make any editing misteaks :)
Write a good ChangeLog that describes why you changed it
Throw away your changes if in hindsight they were no good or just futzing, before they get into the codebase
Get into a frame of mind where you avoid gratuituous changes: every diff should have a purpose, whether it be adding functionality, documentation, or refactoring
Make sure your change list has a single purpose. If your checkin comment has multiple clauses, then you didn't commit soon enough or you should split your change list.
...and your pair make sure you did the RightThing (reworked hacks, formatted consistently, commented the tricky stuff, etc.)
Ensure you haven't reverted someone else's changes (if you're in a situation where the source library can't or won't do that for you).

what's "futzing"? -- AndrewCates

"futzing" = fiddling around with no real direction or outcome. -- jt