Register your domain name - but don't stop at just 1!  If your name is long, or doesn't convey an idea of what you do - register extra domains - get 1 that is short & memorable - use this on your business cards. Get 1 for your yellow pages ads - another for TV & radio. Avoid dashes for anything but keyword rich domains for search engine promotion!

Find a host that understands how to make these domains work independently of each other - to track your marketing!  If you can't track them, don't buy them; unless you want to stop someone else from using them!

Make sure your host is up!  Silly?  No!  You would be amazed how often some hosts go down - pay a little extra for a quality web host if this is your business, and don't get thrown together with "hobby" web sites - your business is probably IMPORTANT to you!