1. Do not date where you work (this rule may be relaxed, in special circumstances. But in general, it's not a good idea. If it ends, you still have to work professionally with this person for many years.)
2. Do not date someone who is married. "Separated" is still married. Until they are divorced, they are still married.
3. Do not have sex with them within the first week of dating!
4. Do not 'move in' together after having been dating for less than four months!
5. Do not tell your jealous s.o. about all the people that flirt with you on a regular basis. They will start a fight, and then you'll be left in the middle, crying about how it's not your fault!
6. Do not, after having been told that your s.o. is not invited to a wedding, proceed to include them on the attending response. They were very specifically not invited for a reason.
Ah, coworkers. It'd be entertaining, if it weren't true...