GoDaddy.com, Bigrock.com, Namecheap.com, Netfirms.com & Domainsite.com are few of the Domain Name providers, where you can find your domain name, register yourself and then you can get your domain.
These are some of the good domain providers which i have used.
Simple steps to buy your domains:
1. Need to register on any of the Domain Name Provider Website
2. Use your login details to get your Domain Name
3. Pay for your Domain via, Paypal, Visa Card, Master Card or any of the convenient method applicable.
4. Next step is to choose your Hosting provider.