• Handle = your username.
• Profile photo = the image associated with your handle (username), and the one that appears next to all your tweets.
• Header photo = the image that appears at the top of your profile, much like a banner.
• Fav = short for favorite; also simply called a like. When you click the little heart icon at the bottom of a tweet? That's faving/liking. Use it to save tweets and links for later, or just to give a thumbs-up.
• RT = retweet. That's how you share what other people are saying.
• LRT or RLRT = Last RT or Re: Last RT. Use this to preface a follow-up to a retweet.
• Mention = to directly reference another Twitter account by typing its handle preceded by @. Tweeting at others can kickstart conversation, and your own Mentions section acts as a list of everyone who's talking about you!
• Thread = multiple tweets strung together into a longer statement, composed by retweeting yourself and breaking your paragraphic thoughts into 280-character-sized bites. Given Twitter's character limits, the thread is an invention of necessity.
• Hashtag = self-applied metadata. A way of making your tweets searchable & your account more discoverable by people interested in the same things you are. #savvy

• Brevity: 280 characters is a challenge (but a cinch compared to 140)!
• Search for & save useful & interesting hashtags.
  
• Make lists— private or public ones— to organize the accounts you follow by main subject, location, or user type. Here are our lists for reference.
• Tag your work: If you're participating in a hashtagged conversation (such as at a conference), include the hashtag in your own tweets so others can see & respond.
• Threading: Multiple tweets on one topic means your followers are more likely to see your thoughts. Thread posts when you have something big to say... but remember to delete @yourhandle from each follow-up.

• To save links, don't rely on favs - use a service like Pocket, Instapaper or Evernote.
• You may prefer to use a Twitter client like Tweetdeck or HootSuite.
  
• Tools like TweetChat and Twubs can simplify participation in fast-moving tweet chats & hashtagged conversations.
• Use tools like Storify to archive & share conversations.
• Twitter's Missing Manual gets deep into the nitty-gritty of Twitter's quirks.
• If you start a tweet with someone's username, only that person and the users who follow both of you will see it. Which is fine, but if you want everyone who follows you to see a tweet, add at least one character before @theirhandle. Current convention is ".@theirhandle take a look at this!" (See photo above)

You can read their great responses here.

By the way, this work is licensed under a Creative Commons Attribution-NonCommercial-ShareAlike 4.0 International License.