Start small, iterate often
One of the biggest pitfalls for developers is trying to do too much too fast. If you haven’t heard of the lean startup, I recommend checking out its concepts here. This movement coined a term called MVP (Minimum Viable Product), which is invaluable for app developers. An MVP for mobile applications is the smallest, most targeted application that you can build while still giving users a strong value proposition. It gets your app in the app store and in users hands as quickly as possible.
Once your app is being used, beat up and thrown away by users (yes, that will happen) you can figure out where to move next. Make sure you utilize a powerful analytics tool or two. These tools will help you figure out what’s great (and not so great) about your live application. Based on the results inferred from your app usage, you can plan your next steps for updates and improvements based on real data.
Keeping up with quick iterations will not only keep your product evolving in the right direction, but it will keep your users happy. For example, if a user has an issue which they see fixed a few days later, this is a good sign that the application is maintained and active (unlike a large segment of apps currently available). Even if the root cause of their concern was a bug, the user will still have a good experience because they feel the app is improving. Your improvements and changes will be noticed by your user base, and in itself is an extension to the user experience within the app.