Moved to Forum: Original Link
Stumbled on this the other day. BasIcally there's a lot of sites, Eg App Nana, Junowallet, which you complete tasks and redeem gifts. Free my apps is similar except you redeem paid apps such as infinity blade 2. Luckily infinity blade 2 is for all devices making it cheaper to redeem and can be completed quickly.
The link below takes you to the site. All you have to do is download some apps from the list provided and run them for 30secs.
No glitches, 30secs on the dot. Then go back to the website and redeem you gift. Each app gives you around 100 credits. Infinity blade 2 needs 800. Plus there's loads of other paid apps available.
http://m.freemyapps.com/share/url/d8a5d314
Mod: Removed referral URL from link
Currently got both infinity blades for nothing. Although get in quick as April sales won't last long.
Hah, now i get how the new apps push up their rankings =)