[Harelin]

When I am working on something and need to break for the day, I try to stop at a point where I am enthusiastic about continuing (i.e. not experiencing writer's block or confused as to how to proceed). This means I will be able to pick up the next day write where I left off, immediately get back into the flow of things, and I will look forward to doing it.

[chris11]

I've also heard that it's a good idea to stop at a point where there are some very easy things that you need to do, even if you might need to introduce some errors to get to that point.

For instance if you were writing a paper, and hadn't ran spelling/grammar check for awhile leaving that as the first thing you need to do the next time you start work would be a good idea. That's an easy fix that doesn't require much thought, but gives you the immediate feedback of getting something done.