I feel silly writing a guide to sending me instant messages, but bear with me, I have reasons. If you’re going to PM me on Head-fi, MacTalk or any other forum I frequent, chatting with me via instant message (MSN, AIM, etc.) is more efficient. You can find my IM details in my forum profile.

Here’s what you should do:
1. Your first message is best something like: “Hi this is X from whateverforum.com. Have you got a minute to chat about something-in-particular?” Then I don’t have to ask you “Who is this?”. I think this is especially good if one of us is buying something from the other, as the negotiations can be done very quickly.
2. If I don’t reply (at any time) it’s because I’m AFK or have been interrupted by something important. I’m not ignoring you, don’t panic. If I’m at work, you’ll usually get my auto-reply in that case.
3. I very rarely chat daily to people, except very good friends. IM’ing me “Hi, how’s it going?” every time you see me online is too much. Really, I don’t have anything interesting to talk to random people about unless it’s very specific, such as headphones and hi-fi, Apple Mac computers or very intense spiritual topics (don’t go there, seriously). IM’ing me with a specific question or topic is cool, just as you might PM me such a thing on a forum.
4. If you want to talk about Apple computer stuff much, try #apple on irc.moofspeak.net.