Since instant messaging can be an intimidating and overwhelming medium (try talking to but three friends at one time...), it may be a good idea to get in contact with somebody by other means before sending them an instant message. Send them an email asking whether IM is okay or call them, maybe. I don't think this is necessary, however.
More Email Quick Tips
Introduce Yourself When Sending an Initial Instant Message
More and most importantly, especially in a business context,
- introduce yourself in the first instant message
- briefly
so the correspondent can put your sudden appearance in context. Sudden questions from people unknown about things you have never heard of popping up on the screen out of the blue ("how much is saturday after the trucks have left?") are hilariously amusing, but only once or twice a week, and your message might be the third of this kind...
While many instant messaging programs have an archive that allows people to find out who you are and what you have been talking about in the past, it is usually a good idea to introduce yourself, even more briefly in subsequent conversations, too (especially if you have changed your nickname!).
