How to Tweet Someone on Twitter

To send a tweet to all of your followers, start typing in the box at the top of Twitter's home page. Press "Add Photo" if you want to insert an image from your computer, and click "Tweet" to send the post. A single tweet can contain only 140 characters, and each image or Web link you add counts as 22 characters. Your tweets automatically show up in the timelines of your followers, while everyone else can see them by visiting your Twitter profile page.

Even if you have only a small group of followers, you might discover a sudden, short-lived fame if your post is widely retweeted. Retweets appear in the timelines of everyone who follows the retweeter, so if a popular account retweets you, thousands of readers might find their way to your profile.

To reply to a friend's tweet, click the "Reply" arrow beneath the tweet. Replies usually appear only in your friend's timeline, but they aren't private -- anyone can see your replies by visiting your profile and clicking "Tweets & Replies." If a third person follows both you and the person you reply to, however, your reply will show up in the third person's timeline. To make sure a reply goes out to all your followers, insert a period as the first character, prior to your friend's username.

Mentions work similarly to replies. To mention someone in a tweet, type the person's username, starting with "@." If your tweet begins with the username, the tweet behaves like a reply. Insert the name in the middle of the message to broadcast to all your followers instead.

For example, the tweet "@eHow Thanks for the help!" would not show up in your followers' timelines unless they follow @eHow. On the other hand, add a period or move the name -- ".@eHow Thanks!" or "Thanks, @eHow!" -- and all your followers see the message.

For the most part, Twitter is an open platform -- you can follow strangers, celebrities and companies, and even reply to their posts, without them following you in return. To start a private conversation, send a direct message with the "Message" button on a friend's profile page. Twitter allows you to send DMs only to your followers, so if you have a private message for someone who doesn't follow you, use a mention to ask for a temporary follow.

Twitter's 140-character limit grew out of the length limit of text messages, and even in an era of laptops and smartphones, you can still send tweets through SMS texts. Add your cell phone number on the Mobile page in your Twitter settings to link your account. Afterwards, send your tweets to Twitter's phone number -- 40404 in the United States. A few carriers including AT&T and Verizon also support including images in your texts.

If you do have a smartphone or tablet, skip the cost of texting and download Twitter's app instead. The app supports posting tweets, writing replies and sending direct messages, as well as reading your timeline and checking out other profiles.