Maybe i can help because i have my Webhosting Business.
1. Buy a Domain like .com or .net. Can very from seller to seller. I sell .com for 7.95 for a year. Namecheap.com is a Good site which sells for 8.88 but look for COUPON codes and you will get a .80 cents discount coupon and Namecheap as great Service and what more you get WHOIS PRIVACY free for 1st year.
2. When you buy domain, you will be asked something called "NAMESERVERS". If you have buyed hosting already, you host will give you NAMESERVERS which in most cases are
ns1.*hostdomain*.com
ns2.*hostdomain*.com
You will need minimum two nameservers, PRIMARY AND SECONDARY. A host can have more of them aswell for differnt servers.
3. When the Domain is registered, you can either park it for the timebeing or enter the HOST's Nameservers. Enter Nameservers and you are done.
4. Since the Domain is new and just registered, the first DNS propogation will be like done in most cases under an hour.
5. After that, if in case you are unsatisfied with services of current Webhosts, all you have to do isbuy hosting from new hosts and enter their Nameservers in the Domain Control Panel.
DNS changes can take upto 24hrs.
Hope this helps. BTW if you need hosting, contact me.