The first step towards posting the perfect tweet is understanding the basic elements that make up posts on Twitter. Basically, tweets are just text. Not even very much text -- while SMS text messages support 160 characters, Twitter posts have to fit within the more rigid confines of 140 characters.
Certain letters typed into a tweet can change the form of the message. For instance, typing a Web address like howstuffworks.com (even without the http:// protocol) will create a hyperlink. That's easy! If you type in the Twitter handle of another person with an @ symbol in the front of it -- for example, @HowStuffWorks -- that's called a mention. Twitter users can see every tweet they're mentioned in. The mention is a great tool for posting Twitter messages because it adds context to a tweet. Suddenly, a vague reference becomes an explorable reference to another person on Twitter.
The mention has a second function that changes the way tweets are routed to your followers. Twitter includes a "reply" button that can be clicked below any tweet. This places a person's name at the beginning of your tweet and is called a reply. This is a bit more like a personal conversation than a regular tweet. The message is still public, and anyone can see it by viewing your profile. However, it won't show up in your followers' feeds unless they are also following the recipient. Sometimes Twitter users want to begin a tweet by mentioning another person. But if they simply wrote "@jill and I just ate lunch. Yum!" only those following the poster and @jill would see the message. A common workaround to this limitation is to put a period in front of the @ symbol: ".@jill and I just ate lunch. Yum!" That tiny dot of punctuation ensures that all your followers see your tweet, even if they don't follow @jill.
There are two more important elements that go into good tweets: images and hashtags. Attaching a fun or interesting picture to a tweet is one way to share something of value with your followers. Many Twitter clients include built-in utilities for uploading images and inserting links into tweets. Web sites like Yfrog and Twitpic allow you to upload an image and will provide you with a short link to insert into a tweet. You can also set your preferences within these apps to post directly to your Twitter feed. Hashtags, like @mentions, are a way to add context to a post. Hashtags are used to denote a trending topic on Twitter or to create a theme for a series of tweets. Hashtags are added with a # followed by text: #academyawards, for example. Twitter's search can pick up trending topics that aren't contained in a hashtag, so they aren't as important as they were when the service first launched. They're often used for jokes or to convey specific emotions rather than as tools to popularize a topic.