First step (important one): Have an android device or iphone 
Second step: enter the below page for downloading and installing a software called freemyapps
http://m.freemyapps.com/share/email/47eb4c21 
Third step: After installation completed, earn credits by install sponsors' apps to redeem for giftcards
And I'm surely that you can get the $25 giftcard for about 3 days :D
PS:  Change your IP address for more sponsors' apps