How can I increase my mobile app's ranking to the top of the Google Play store?

In my opinions, no ‘magicians’ know the correct algorithms used by Google Play store for ranking the apps, but experts tell there are certainly few ranking factors which play the most important role in ranking of your app in App Store.

Downloads– The number of downloads of your app reflects the popularity of your app. The more downloads your app has, the more chances it has of being in the top search results.
App Reviews and Ratings– Quality is sure a factor Google gives importance to and it reflects in the search optimization. Apps having more positive reviews and better ratings are given a much higher preference to the apps having lower ratings by users. Less popular apps with lesser downloads but better ratings are ranked higher than popular apps with a lower rating.

Long Installs– For how long your app is kept installed by the user in their mobile is surely a factor which Google consider. Google seems to track the time of app installation and give positive points for longer installed apps.
Uninstalls– Instant uninstallation of the apps after being downloaded or uninstallation of the app after the latest version is released will certainly get your app bad ranking in search results.
Social Links– Apps on the play store are also linked with Google +1 boost are called as recommendation. More the +1’s or recommendation, better it is for the app.
So, while creating or uploading your app on Google play store you’ll have to take care of the following things to optimize mobile app:

App Title. The name you give to your app can work both in positive and negative ways in the app search box. If your app title has the right keywords related to your app, it increases the chances of getting discovered by users in search. Use your main keyword in the app title.

Description. Short and strong should be your policy while giving the description of your app. Describe what your app does. Do not forget to include social proof such as awards or got covered by leading media agencies. Only a few lines are shown in the description. So it is recommended to use fire words. Do add your target keyword 3-4 times in the description. Do remember that first 167 character of your app description becomes the Meta description for search engine.
Use AppSally. AppSally will help you with the best targeted keywords so that you can get more visibility and installs in Play Store.
Importance of Screenshots, Videos, and Graphics. Screenshots of the app and its design are the way a user gets to see what will he get after downloading the app. Uploading high definition screenshots of all sizes will surely increase the chance of a user downloading your app.

Google app store also allows the developer to show video of the app in the details page. With this feature, you can showcase the distinct features your app has and can convince the user to download your app. Graphics play an important role in App store. From app icon to graphics used to showcase app is one big thing that catches the user eyes and makes them stick to your app.
Reviews, Ratings, and User experience. The rating and reviews of your app is directly related to the search ranking of your app. If your app has a 5-star user rating and positive reviews then you stand a higher chance of being shown in the search result when a user searches for a particular category of app in which your app falls.

Anyway, these are only some of the tips which has helped numerous app developers & businesses to improve the ranking of their Android app in Google play store. So, hope this will help you too!