There are some important tips to promote your android apps.
1 = Offer App install using Facebook ads:
The best way to get a lot of installs is using paid medium such as Facebook ads. Facebook offers advertising for app (Both Android & iOS), and you can target users based on various factors such as age, location, mobile OS and many more. If you have an email list, you can use that to target your ad to a particular list.
2 = Submit to multiple store:
Try to submit your app on multiple stores. Google play store is the popular, but there are many others such as Amazon app store, which is good too. Here are some important app store where you can submit your mobile app:
This has been the best way to get people to download premium apps. The free apps get the user base and then it will tend the user in buying add-ons or the full version if he likes it. Or you can simply launch a free app with ad and promote an add free with some advance feature in your premium version.
4 = Promotion through review:
The best method to market your app from my experience is through content and reviews.
5 = Promoting through free content:
It’s a startup voting community that ranks apps submitted every month end. If your app idea is good, then it might even be on the site front page for a month if it gets enough votes. The site is also a good option if you have the same app for different operating systems because they accept Windows,iPhone and Blackberry apps as well.You can try this if you want to get an initial boost of downloads.
6 = Promote on YouTube:
Make a couple of YouTube videos showing how the app can be useful to people or entertain them. Try to make the video using a better clarity and understanding which is also worth sharing.
7 = Use social media:
Social media can be useful sometimes. Submit your app to social media like Stumble upon,Reddit, Digo, etc.
8 = Press Release:
I have very limited information regarding Press-release promotion. Though, if you manage to get into one of those PR agency, who sends out the newsletter to Techies and Bloggers about latest Android apps, getting into one such list is going to be very beneficial.