The Basics
Navigate to http://twitter.com/ and select the green "Sign up now" button on the right hand of your screen,
The first field you will be asked to fill out is your full name. By using your real name, you increase your relevancy and familiarity with your followers.
Next, you will be asked to select a username. Try to pick something that describes you - whether it's a nickname, an interest or a hobby. I chose the name 'n00binat0r' to make sure everyone knows that I'm new to Twitter. This will be the name your followers use when sending @replies, direct messages, or Retweets. It will also form the URL of your home timeline. A preview of that URL is shown below for the username @n00binat0r.
Please note: You can change your username in your account settings at any time, as long as the new username is not in use. Usernames must be fewer than 15 characters in length, and cannot contain 'admin' or 'twitter' in order to avoid brand confusion.
Once you have selected an appropriate username, you will be asked to enter a password. Be tricky! Make sure your password contains letters, numbers, and symbols. Please do not use a password based on a word found in the dictionary.
Once you have entered a sufficiently strong password, please provide an email address. We use this to confirm your account before you can finish the signup process.
Finding Sources That Interest You
Because Twitter is more useful and fun when you're getting regular updates relevant to your interests, we ask that you select some of your interests from the left-hand side of the screen. This helps us suggest accounts you might like to follow. Each time you select an interest, a list of suggested users is generated. Clicking the 'follow' button next to a user's name will add them to the list of users you are following. This is indicated by the number in the green square above the list.
Tip: Create a 'following' list that's as varied as your interests. After you've followed users suggested in one area of interest, select another and find more sources to follow! When finished, click the blue 'Next: friends' button in the lower right hand side of your screen.
Here's where it gets personal: If you choose, Twitter can scan your email address book in order to find contacts that are also using Twitter. It's a fast and easy way to find your friends. Simply type your email address and your email password into the boxes, then hit 'Find friends.' Twitter does not store your login, and we will not use your email address without your permission.
When the scan is complete, Twitter will show you a list of the friends and colleagues it found in your address book. You can choose to follow all of them by selecting the blue 'Follow All' button on the right hand side of the results, or if you'd like to see updates only from specific people, you can choose to follow your email contacts individually using the grey 'follow' button next to their information.
Once you have selected the friends and colleagues you wish to follow, click the 'Next: others' button at the bottom of your screen. A box will pop-up with your remaining contacts, those who are (sadly) not on Twitter. If you would like to invite them to join Twitter, simply check the boxes next to the contacts you wish to invite - or click "select all" at the top. Please remember that if you select all your contacts and proceed, it will invite all your contacts.
After you have searched, found, and followed any remaining friends or colleagues, click the blue 'Next step: you're done!' button to finish the sign up process. You will be taken to your home page, known as your timeline, where you can now share information via Tweets, as in the example shown below:
Press 'update' and you've successfully posted your first Tweet. Congratulations and welcome to Twitter!