Checking for available names for a blog

Hello! I am thinking of starting a blog on Internet related to photography. How do I actually buy a website, where do I have to pay the fee? I also want to know how do I check if the name that I have in my mind is a valid name for a website. Are there any websites which tell me if its a valid name or not? And by the way who is the governing body to which I am supposed to pay the fee to have my own website/blog?
