Given how few new apps people download on mobile and the steep drop-off within apps, getting Day 1 retention right is critical.
Given the cost the effort required to get people to download your app, Day 1 retention is a critical metric.
Day 1 Retention is the fraction of people that return to your app one day after install. If you don't get Day 1 retention right, the rest really doesn’t matter.
So how do you get Day 1 retention right? Spend [a lot of] time working through the first time experience for your apps. How can you get people to come back the next day? Get that over 50% and then you can tackle the next metric...