Following conventions doesn't make your app conventional. Embrace Apple's design sensibility.
Apple's built-in navigation models provide organizational solutions for most apps. Understand the pros and cons of each, and choose the best match for your app: flat pages, tab bar, or tree structure.
Storyboard your screens to plan a clear flow through your app. Do big-picture thinking on paper before jumping to pixels.
Start ugly. Begin with a primitive prototype app before starting to code with your full design.