Head on over to their blog, subscribe to their RSS feed and leave a constructive comment at their site in order to be entered into the contest. Winners will be announced on the 29th of April.
Do head over to tfgblog, specifically this post for further details. And Good Luck!
PS: Guys over at tfgblog, don't forget to add me to your blogroll :)
PPS: If you are feeling unlucky, or left out (after all, the contest is open for those living in the States or Canada), GTA 4 is available for pre-orders at Play-Asia.