You can use Twitter to connect with your friends by sending them an invitation to join Twitter. By inviting your friends to become Twitter contacts, you're letting them know that you're on Twitter and that they can follow your updates by signing up for Twitter themselves.
To send an invitation during the Twitter registration process, you can import your contacts from your e-mail address book and invite them to use Twitter. (Just select your contacts you'd like to invite on the Why Not Invite Some Friends? screen and click the arrow.) But if you've already set up your Twitter account and would like to invite friends, follow these steps:
On the top navigation bar of any Twitter page, click the Who to Follow link.
The Who to Follow page opens with two panes. The right pane has the Invite Friends option
In the Invite Friends text box, enter the e-mail addresses of the people to whom you want to send an invite.
Separate e-mail addresses with a comma and a space.
After you enter all the addresses you want, click Invite.
You're done!
You can always e-mail people you know whom you think would most enjoy or benefit from Twitter, sending them a link to your Twitter profile and writing a note explaining what Twitter is. Many people choose this approach when they first join Twitter so that they can keep the invitation process personal.