Some may call it ASO (App Store Optimization) but in simple words it's getting the basics right.
1. App Title — Use the title to convey the most important function of your app. Your app's appearance in search result is heavily dependent on this. It is recommended even more if your app name is not a regular known word. For example, Whoots or Pluck or Mosaic should ideally be renamed as “Whoots — Send Gifts”, “Pluck — Make Friends” & “Mosaic — Enhance Photos” to make it work better
2. App Description — This is your best chance to impress the app store’s search algorithm. Use the most relevant, crisp description covering each keyword your users are likely to associate with your app. Don't use keywords for the sake of it — try to make it a part of your native description. Do not repeat words (Google Play recently changed its content policy to disallow this).
Tip: Use tools like keywordtool.io to identify the most relevant keywords for your app.
3. Screenshots — Nothing works better than a good visual impression. Select the best looking screens of your app. Also create custom screens to showcase your features in a visual way.
4. App Icon — Make it iconic. Icon is the first thing a user would see and it has to stand out. Don't clutter and don’t write too much text on it. Also try placing your icon among various app icons and do a look test.
5. Include Video — Google Play allows you to add a video. Works really well if you have a paid app and someone wants to be 100% sure before spending a money in which case video comes to the rescue. 20 seconds video can narrate what 4000 word description can’t.
Tip: Create free product videos at powtoon.com
6. Reviews & Ratings — Make full use of your network on Facebook, Twitter & close friends to get them review & rate your app. Reviews play an important role in improving your rank. Get your friends to review your app (don’t force them to post only positive review as that's your best chance to get some real feedback). Ensure that you reply to every negative review on Google Play. Replying to review is not possible on Apple store.
Tip: Don’t forget to check out the sentiments of your users’ reviews at appbot.co
7. App Reviews on Blogs /Review Sites— Get as many bloggers and journalists to review your app and post it on their blogs and link it to the App Store from there.
Tip: Download the sheet of all app reviews sites with their contacts from j.mp/GetReviewed
8. Incoming Links — Google Play gives great importance to multiple incoming links to Play store App description page. It tells Google that your app is popular and it bumps up the rank over the due course.
9. Submit your App Everywhere — For Android, Google is not the only App store available.There are over 50 stores worldwide including AmazonApp Store. Make sure you that you submit your app everywhere.
Tip: Submit your app for Facebook App Center .
10. Create Hype/PR — This is the trickiest but can prove most effective. Get influencers to talk about your app. Get some big sites to cover your app. Hype alone can give you hyper growth in initial phase. Just network.
11. App Indexing – Get your app indexed with Google. Now Google supports both Android & iOS. The direct impact of indexing is not yet seen on ranking but it would surely bring in organic incoming traffic which helps in improving the rank eventually.
12. Reduce App Size: Ensure that you keep your app size below 5MB as it will result in better conversion from Play Store View to download thus prompting Google to assume that it’s a good app. Optimize your app using Proguard, Lint, 9patch Images, PNG optimizers etc. And there is a little hack (not officially verified but it works) — Integrate Google+ sign in your apps and webpage to allow OTA install. Play Store gives extra importance to apps using this feature.