Google is very kind to it’s users and giving away free Google Play store credit via Online Survey. So basically you don’t need to do any thing apart from giving your opinion for Google products. These surveys will be only for smartphone users with Android operating system residing in United States of America only.
For this purpose they released a app for Android users known as Google Opinion Rewards and of course the app will also be free of cost. After installing the app you need to setup few things like your name, address, mobile number etc. After this setup all users will get one survey at-least every week and upon successful submission you will get minimum of two dollars Google Play store credit. Of course the cash amount will vary depending upon the survey ass well as users location.
Questions will range from giving your honest opinion about Google products or simply choosing the new logo for any new product. So all in all you will get some thing out of nothing and that too from the device you have in your pocket all the time.