If you have an Android smartphone, you need to install the Google Opinion Rewards app! This will occasionally pop up a notification depending on the areas you visit and ask you a simple multiple choice question. Answer them honestly when they pop up and you will be rewarded with Google Play Store credit. You can easily accumulate upwards of $20 per month, meaning you can get premium apps for free!
A lot of the questions that come up for me are asking if I've visited certain businesses and in most cases, I have not. Even answering "None" to these questions usually results in a payout of $0.10.
Another tip, make sure to check out the "Games" tab in your "Play Store" app and scroll down until you see a section titled "Games on sale". More often than not, you will find a lot of premium games on sale for $0.00, yup, completely free!
Happen to be in the market for a new smartphone? Be sure to research the Google Pixel, Apple iPhone and Samsung Galaxy smartphones. The Google and Samsung are Android-based phones, which I personally prefer as I like to support open source initiatives.