where to start

I'm a php/mysql webdeveloper and I would like to start taking on freelance work. I have no idea where to begin. Do I need to form a company? Where do I begin with taxes?

And any other suggestions of how I do this would be appreciated. I get offered freelance work frequently, but I never take it.

Thanks in advance, and if there is a thread that covers these already, could you please give me a link to it. I searched, but I didn't find one.