A few red flags I've encountered:
1. Being asked to describe your job
2. Being asked to document every task, meeting, phone-call, etc. you perform in one day.
3. Being asked to train the new guy on certain facets of your job.
4. Lots of closed door meetings and/or doors slamming
5. People staying late/arriving early that usually are clock-watchers.
6. Weird new people showing up @ 5PM (interviewees)
7. Resumes on the fax machine
8. Jobs posted on Craigslist that look eerily like yours or your co-workers.
9. Constant phone-calls to the AP department (by rude and demanding people).
10. The boss constantly experimenting with new software, procedures, etc. (and touting them as the next big thing that will save the company)
11. COD deliveries
12. Poorer quality of purchased materials arriving
13. People who once didn't care about how things got done, are now showing an interest in learning everything.