There are a lot of ways to promote your app, depending on a budget:
Facebook ads
AdMob
Reviews
Google Adwords
Press Release
Promotion campaigns, like App of the Day
ASO etc.
I create a flashlight app.. And I'm not getting any downloads. What can I do to get more downloads?
Mod Edit: Link removed
Free or do you charge for it?
What platform?
Have you advertised it?
What's special about it?
The simple answer is, write a better app and publicize it. Unless it's free it will have to be very good - why would people pay for something they can easily get for free?