Presentation is critical to any mobile application. Although the data tier, web services, and API are important, without the presentation tier, there's no way for the user to interact with your service.
This much is obvious, of course, but it's also important to plan your presentation as well. Users appreciate functional apps, but they also appreciate apps that are well designed and even beautiful. Enterprise apps might not always fall into the beautiful category, especially if there's a lot of data entry, but a well designed app that guides the user in their interactions is something that should be desired.
There's no possible way we can cover every possible presentation technique in this chapter, or even in this book; there are volumes dedicated solely to this part of app development alone. Having said that, we'll touch lightly on some of these basic concepts:
Mock-up design tools
Libraries and frameworks
Common patterns (MVC, publish/subscribe, observables...