How do you know when you've found it?

Let's say you're a hiring manager, and you've figured you need to add a new member to your staff. Let's also say that you're pretty savvy on the recruitment process, you've done your research and you know what this person will do (you even wrote up MBOs), and you have a spiffy, new job description. You KNOW what you want.

Flip this around.

Now, let's say you're in job-hunt mode. Yesterday, you came to the conclusion that you've had enough, or that you want to do something new, or a combination of the two. Have you written up what you want to do next?

Most candidates don't take the time to do the write-up. If you don't know what you want to do next, how do you know which job offer to accept?