I hope you have undergone
Connecting to SQL Server over the Internet
in MSDN.
I have tried the same long back and telling it is very difficult to achieve if you dont have your own server. You need to get rid of network, firewall and SQL server. Also you need to get in touvh with your ISP for port opening. Also make sure that your are fetch your public IP Address. It took almost a week to make thi shappen.