How do I start an iMessage conversation?

[islaj]

My friend started one with me and now our phone text conversation is an iMessage one, but I don't know how to start it with other contacts, or can I not start it because they may have not set up the newest software and if they had it would automatically be iMessage?

 

[fullojellybeans]

If the other contact has the blue chat bubble next to their name when you type it in that will become an iMessage

 

[AIP5]

You just find a contact who has iOS 5 installed, and message them. It's very simple, and it somehow just works.

For non iPhone iOS 5 people, I believe it was their e-mail address. Though, I'm not sure. I've been iMessaging iPhone iOS 5 people today.