Found this article on Twitter etiquette and thought I would share it. Some of my favorite quotes:
10. Try to keep within the character limit.
13. Plug moderately.
Now, you already have a phone, an email account, a blog—but what about the moments too small to blog? (Snacking on pretzels.) Too insignificant to email? (The twisty kind of pretzels.) They’re happening every second! How can you share the moments between the moments worthy of note? Enter Twitter.
I’m not sure how you could exceed the character limit, but as far as I’m concerned as long as you can fit your tweet in 140 characters or less and don’t have to use two tweets to convey the message it’s fair game.