Easy. Windows Live friends will add you to their contact list the same way they would add any contact. But there is one catch: you both need to be running your Messenger’s latest version.

Click here to get your Yahoo! Messenger.

To make it easy, if one of you is running your brand-new version and invites the other, who isn’t, the one who isn’t will be offered a link to download their latest version right in the invitation. Nice!