The contest is only open to U.S. residents who are 18 years or older who use Twitter. If you are eligible you can keep reading on how you can enter.
In order to enter you need to go to follow @GooglePlay on Twitter. Next select something you like from the Play Store (app, game, move, music, television show, book or magazine) and Tweet a link of that item to @GooglePlay with the hashtag #favoritethings.
Finally go to the official blog by following the source link and fill out the entry form. The contest is open until 11:59PM PDT on April 24, 2013 so be sure you don't miss out.
Google has even provided an example if you need inspiration:
"My favorite movie on @GooglePlay is Toy Story https://play.google.com/store/movies/details/Toy_Story?id=c3986gGp3Qs #favoritethings."
We are a little surprised that Google chose to use Twitter for their contest instead of Google+ but hey a contest is a contest and we wish everyone who enters the best of luck.
source: Google Play