To enter the contest, you need to go to the Google Play Twitter site and follow @GooglePlay. That seems easy enough. Next, select something that you like in the Play Store. It could be any app, game,movie, music, television show, book or magazine. Tweet a link of that item to @GooglePlay with the hashtag #favoritethings. Google's example is "My favorite movie on @GooglePlay is Toy Story https://play.google.com/store/movies/details/Toy_Story?id=c3986gGp3Qs #favoritethings."
Finally, you go to the official entry form at the sourcelink and fill it out. You have until 11:59PM PDT on April 24, 2013 to complete your entry. Good Luck!
source: GooglePlay via AndroidCentral