The SEO blog has produced guide on how to use Twitter by identifying different usecases.
General how to use Twitter advice:
* basics
* advanced
* even more advanced
Twitter use cases:
* social networking
* blogging
* business
* SEO/marketing
Avoiding Twitter pitfalls:
* twittiquette/twittequette
* safety & security
Please note that every item in this list is made to work as a standalone retweetable tweet. They in most case make sense on their own and are short enough to get retweeted a few times.