The New York Times recently published this informative article on registering a start-up business  I think the article is a little on the scare-mongering side, but at least it doesn't sugarcoat the importance of the basic legal steps needed to start your own business.  Several times a year I get prospective clients in my office who think that they need extensive legal advice to go into business.  If you're just going to be selling your quilts at the local farmer's market you may need only a brief consultation with a lawyer to make sure you aren't missing some important step.  What I like about this article is that it shows some of those important steps, including choosing and protecting the name of your product or business, choosing your structure (see this site from the Small Business Administration for some information on business structures) , getting a federal tax ID (and you'll probably need a state tax ID too).  Don't forget checking with your county and city as well to see what permits or licenses you'll need to operate a business.  Some cities require a license to operate any kind of business, while others only license certain types of business operations.

Here in Colorado, a great place to start for some of the initial research on names is the website of the Colorado Secretary of State.  While a name search there won't list every business in the state, it will alert you to other businesses that have registered their company or tradename in the state. 

But don't be fooled -- merely registering your tradename or even filing articles of incorporation or articles of organization aren't enough to protect your company name or personal assets.  Maybe you don't need to protect either, but if you do you'll need competent legal assistance from a business planning attorney.  First, though, you can educate yourself with some of the sites mentioned in this post.