Did you know that more than 80% applications are only being used once before being deleted?
If you want to occupy solid market positions, you need to encourage users to enter your app again and again, using promotions, daily rewards and so on.
The last but not the least is a so-called CPI promotion.
It is a great chance to boost your app and speed up the number of downloads. Usually such traffic is attracted by professional companies, like [b]KeenMobi[/b], which has a great base of real users. The average fee is around $0,09 for the install. 
The higher the number of downloads is, the better ranks your application occupies. This attracts new users and stimulates further downloads.
As you see, there are multiple instruments, when it comes to marketing and promotion of apps at Google Play Market. They can be both free and paid ones. By using services of skilled and experienced companies you will get a guarantee of your app’s success.