If you are planning to build a web site right away for your domain, it is often easiest to register the domain name with your chosen web host. If you decide to host and register separately you will want to choose a domain registrar with a quick DNS set up time. Usually this process can take as long as two days to get the domain name and web host in sync.

You've got to be kidding me.

There is NEVER a good reason to register a domain with your web host. If the host you pick sucks, you're screwed. Plain and simple.

For "building a website right away with your domain", register the domain, pick the host, change the DNS entries to reflect the host, and while propagation takes place build your site. Why make it any more complicated than that?

I agree, always host you domain(s) separately from hosting. You can have a new domain up and running virtually instantly nowadays, just point you DNS to your host when registering. I've had new domains live and working within and hour on occasions.