For example, when you are leaving your employer should you send an email to everyone saying "I really loved working with you" even though you didn't know the names of half of them? Is it rude to send one only to people that you REALLY know? Or what if you mean to send it to everyone but you forget someone? Will they feel ostracized?
Or how about that all time favorite--- going-away parties? Who gets invited? Should you even have one? Or, god forbid, what if no one wants to throw one for you? Does that mean that you were really a horrible boss and co-worker even though you didn't think so? How do you hold up your head in that situation? Do they think you hated them?
And how about moving all your stuff out of the office? Is it appropriate to ask the mailroom guy to help you even though you ignored him for the 10 years that he delivered your mail? Or should you just do it yourself in the dark of the night? (But then what happens if Security thinks you're stealing stuff?). It's difficult to know how to handle these things. It would be so much better if someone published rules.
Finally, there's "Staying in Touch" etiquette. Is it OK to call people at your former office once you've left? And what do you do if they call you? I've personally subscribed to the theory that I needed to "detox" for awhile, so I am trying to lay low for a period of time. And, of course, that is so much easier when you have a Blackberry that doesn't have anyone's phone numbers or email addresses in it.
But after awhile you find yourself thinking, "Oh, I must remember to tell Person X about this when I see them next week". Only you're not going to be seeing them next week because you no longer work with them.
So, after a period of time (which my former-athlete husband calls the "time out"), I think it's perfectly acceptable to reach out to those folks you worked with that you really enjoyed. Just try to keep the conversation about non-work matters. There's nothing worse than someone who has physically left but is still mentally engaged. You need to be thinking about your future life and you can only do that if you don't revisit your past every time you see former colleagues. It's healthier, too, because your blood pressure won't skyrocket.
I think you'll be surprised how much you'll learn about former colleagues as people once you don't spend all your time talking about work matters. I had no idea that one work friend just bought a new house. How could I have missed that? Probably because I wasn't focused on her as a person. A good lesson for my future relationships once I do go back to work.