I'm starting to meet a lot of educators who want to get started on Twitter, but aren't really sure how to do so. The screencast above is a super simple demonstration that begins at the very start and progresses step by step through the processes of signing up, setting up a profile and starting to find relevant people to connect with.
I recommend watching the full-screen version (just click on the four little arrows that appear at the bottom right of the video there). Oh, and also click on the HD option (also at bottom right) which will render a high definition version for you to view on the fullscreen presentation.
Having watched the screencast after making it, I would add that the advice I give for setting up a bio doesn't necessarily suit everyone. As in, I recommend being open and frank and informative about your line of work and even where you work, but many educators actually keep this information limited to profession and general location. That's up to you really, and how inclined you are to watch your p's and q's whilst tweeting!
But I do think a profile pic and informative bio are absolutely essential if you're an educator and really want to connect with other educators.
A little later, I hope to do a follow up screencast demonstrating how to actually use Twitter effectively and productively. In the meantime, if you've successfully set up a Twitter account and want something to go on with, there is a tutorial I produced here last year which also demonstrates some of the basics but featured the older version of the Twitter interface. That one also demonstrates things like responding to tweets, retweeting, etc.
Hope this helps any of those educator-tweet novices out there!