A bunch of websites offer hints, tips, suggestions, advice, etc. etc. on how to use Twitter.

You can learn something from all of them. Some are better than others. There’s a lot of overlap. Here’s my take on Twitter best practices, after almost two years of using it (@rharris).

Ten best practices for using Twitter effectively

1. Be proactive about what kinds of content you want to post on Twitter. For example, provide links and tidbits that are useful to your followers.
2. Follow users who have relevant posts. Retweet their posts where appropriate, and comment as needed (or possible within the 140 character limit).
3. Update the feed at least four to five times daily, but not so often you are posting irrelevant, mundane or banal material.
4. Use Hootsuite to schedule tweets ahead of time and to track clicks on posted URLs.
5. If metrics on Twitter are important, consider posting URLs only via Hootsuite. This tool provides stats on the clicked URLs, enabling you to see what links are most popular with your Twitter audience. This will need to be continued over some time to build up a meaningful picture.
6. Post your Twitter profile to JustTweetIt and Twellow.
7. Replace the standard Twitter background. You can use one of several skins, or better still create your own and upload it. (See Twitter Background Design How-To and Best Practices )
8. Use JustTweetIt and Twellow to find power users related to your area of interest, and follow them. They can provide useful posts to “retweet.”
9. Use hashtags to allow users to readily find relevant content (e.g., #swineflu, #obama), and encourage followers to use these when discussing relevant topics.
10. Study and follow guidelines on “Twittiquette.”

See also
The Creation of Twitter Best Practices: Round 1
Twitter Best Practices So Far
Ultimate Guide to Twitter - Marketing, Tips, Best Practices & More
Techsoup: Twitter Best Practices

Twittiquette - The Do’s and Dont’s of Twitter
The first 10 Rules of Twittiquette
five steps to good twittiquette
Paul Matson: Twittiquette