If you want to open blog on own domain you should buy it before.
I’m usually looking for domain names on Yahoo
I’m not buying domain names on Yahoo last time.
If you are buying domain name first time you can do it – price for new customers on Yahoo is $9.95 but if you’ll want to renew it next year you should pay $35
This is the reason why I’m buying domain names on Godaddy.com
Price for first time buyer for year is $1.99, price for renewal is about $10, price for new .com domain for current customers is $9.99, price for transfer domain name from another registrant is only $6.99
I’m really contented with GoDaddy prices for domain names