Free apps are nice, but sometimes great apps cost money. Fortunately, Google has a nifty program that gifts you various increments of Google Play credit just for answering a few survey questions from time to time, so you can easily rack up dollars and cents to help you pay for those apps.
Download the app
Quite frankly, that's all you have to do. Download the Google Opinion Rewards app from the Google Play store. It's an app from Google Consumer Surveys, a program for companies and marketers to get a better handle on their demographics.
Tell it what you think
Google Opinion Rewards will ask you a series of demographics questions, like what you political affiliation is and whether you live in a suburb or a city, before it gives you any surveys to answer. This is to help determine which questions are best catered to you. On its FAQ page, Google says it won't allow surveys that "request personally identifiable information from users, such as phone numbers, email addresses, [and] physical addresses."
The app says that all the surveys are anonymous, but the app does need you to log in to your Google account because it has to deposit the Play Store credit into it.
After answering those first few questions, you'll see notifications pop up from time to time to let you know that a survey is ready for you. Questions will range from "Which do you like better?" to "When you hear this company name, what does it make you think of?" with several answers to choose from. You can receive anywhere from 10 cents to a dollar, all of which is dumped into your Google Play account to use for apps, e-books, music, and videos.
Bear in mind that if you aren't seeing surveys after a while, it's because Google doesn't have any surveys available for your specific demographic. Most users should get at least a couple surveys a week.