If you haven't yet and are thinking of taking the Twitter plunge, you'll be joining about about 15% of online people in America who use Twitter, and only 8 percent who use it a lot.

Here are the basics to get you started: accounts are free. Sign up at twitter dot com or on your smartphone.

Tweets are limited to 140 characters. You can follow other accounts, and those show up in your feed.

If you want to mention someone, put an "at" symbol before their twitter handle and they'll see it on their "connect" tab. To reply directly to a tweet just hit the reply button and start typing.

Rob Archer