Instant Messaging Rules of Engagement

Over at WebWorkerDaily there is a post on how instant messaging can make you more productive.  After reading the post and contemplating it a bit...I agree. For me, IM productivity boils down to self discipline. 

After thinking about the post for a while I discovered that I unknowingly have a few silent rules for IM engagement (when I engage), and IM pet peeves (when others engage and don't follow my silent rules):

When to IM

1. When the question I'm asking can be answered in 2 sentence or 2 responses.
2. When a question is too technical via phone and could be better worded through a pre-thought out IM initiation.
3. When technical information can be utilized by the IM client (e.g. sending a link versus trying to spell it out over the phone).
4. When you want to document the conversation for legal purposes or future reference (if the IM client logs conversations).
5. When the recipient is not in the building and you need to share your desktop with them because a visual is better than a long winded, confusing description (if the IM client allows desktop sharing)

When not to IM

1. When the IM subject is controversial or emotionally charged (in a bad way). Obfuscation of the text can only make things worse.
2. When what you are going to write would get you in trouble when viewed by others (e.g. somebody is standing over the recipients shoulder or IT logging it).
3. When the person sits within 20 feet of you (duh?).

A couple Instant Messaging Techniques

1. Do an initial IM to remove the element of surprise for a complicated question or issue, give the receiver 30 seconds to mull it over. Follow up with a phone call.
2. Send technical information (Web link) and call immediately.

What are your Rules of IM Engagement or techniques?