Ask HN: How do I know where my mobile downloads are coming from?

Hi everyone,

Last month, my company launched its first mobile app. The team has been promoting the app all over the place (FB, Twitter, forums, email, Ads, PR, etc). As a result, we have grown to a few thousand users, which is awesome.

The problem is that we have no idea where our users are coming from. We don't know what our most effective marketing channels are. We don't know which marketing campaigns are most effective in bringing users.

How do you deal with this problem? Please list the pros and cons.

Thanks!