Here are my preferred methods of communication:
- Email - Non-emergency. I can read it any time and get back to you whenever. When I get email, my phone does not vibrate or make noise.
- Instant Message - Non-emergency. This is more of a real-time chat when I'm not busy. When I get an IM, my phone makes a short, quiet beep that I'd only hear if I was available to chat anyway.
- Text Message - Emergency-ish. You want to talk to me now, but it's not Urgent. My phone beeps and vibrates when I get a text message.
- Phone call - Emergency. You need to talk to me now. It may or may not be urgent, but you don't want me to ignore you. My phone vibrates and plays a loud song when I get phone calls.
It's interesting. Younger people just default to text messages. To me, a text message is like a page (from the old one-way pager days). And, to me, pages mean something bad is going on: a server is down, a friend is hurt, etc. I'm getting more used to getting text messages as if they're Instant Messages, but I think my list above just makes sense.