Buying your domain name seems pretty simple on the surface, but there a few things you should keep in mind when shopping. While there are no limits to the number of domain names you can purchase and forward to your hosted website, you should have a primary domain name that you tie your analytics and marketing.
There are many domain extensions (.com, .net, .hosting) to pick from, if possible the .com is usually something you'll want to own. With the many new extensions available or waiting to be released, you can pick up some unique options, such as www.karmicvisions.graphics. Here's a good link for a listing of the different top level domains.