It is advisable to create multiple Twitter accounts focused on your different interests. You will find that users of one topic may not be interested in other topics, or even turned off by them. But there is a slight problem with creating more than one account. For each Twitter account you need a unique email address. Who wants to create a new email account for each Twitter account? That is way too much to manage.
Gmail offers an elegant and simple solution to this with no setup AT ALL. If you already use Gmail, and most people do, you can create pseudo accounts in Gmail just by changing a specific part of the email address. Now be careful here, you can't just change anything... Pay attention to the modifications that are allowed by looking at the examples below.
Let's pretend for our examples your Gmail address is: firstname.lastname@example.org
Gmail has a couple of interesting tricks that you can use to instantly modify this address.
Gmail Trick #1: Gmail ignores all periods that come before the "@". So just add a random period into your username. The following are all considered identical by Gmail, but other websites will consider them to be unique.
If you need a unique email address to register a second or third Twitter account this solution is easy and quick. Again NO setup. Just keep track of which account is which.
Gmail Trick #2: Gmail also allows you to create alias accounts by adding a "+" and another word before the @. The following are all considered identical by Gmail, but other websites consider them to be unique.
The second version is my preferred method, it allows you to make more memorable alias accounts.
HINT #1: Before you try this on Twitter or elsewhere it is easy to test. Load up Gmail, create a new message and in the "to" line type in your new fake/alias email address and send it to yourself. You should know in seconds if it worked.
HINT #2: This also works with Gmail accounts even when your email is attached to an organization. So if your email is email@example.com or firstname.lastname@example.org as long as Gmail/Google Apps are behind the scenes it should work perfectly, but test to be sure.
HINT #3: Consider using a password manager to manage multiple accounts at the same site. I use Lastpass and I am quite happy with it, but there are several good products available. Look into them and use one of them.
Check out the Twiterversity guide.