GoDaddy
While I tend to like smaller, more “boutique” service providers in general when it comes to a registrar for your domain names, my favorite is GoDaddy.
Setting up an account is free and their rates for the various services are great. Once you are set up, management is clear and easy.
My one complaint is that they are BIG on up-sells. So when you do make a purchase you have to wade through a ton of offers before you get to checkout. Not a big deal and in reality it probably takes less than 30 seconds . . . but I thought I'd give you a heads up!
Note: Your registrar is where you register and manage your domain.