- Create an application definition statement.
- Reduce your app's feature set to just the essentials.
- In the UI, display only the most important items.
- Showcase content.
- Place secondary options in separate screen or popover.
- Make tap targets fingertip sized.
- Vary control size based on usage.
- Provide adequate spacing between controls.
- Provide immediate feedback.
- Use texture and depth to give a tactile Look.
- Design controls to stand out from artwork.
- Smooth transitions.
- Communicate status and process.
- Match the user's gesture.
- Be realistic.
- Use sound.
- Communicate status.
- Enhance interactivity.
- Label controls with their resulting action.
- Be clear and concise.
- Use user-centric language.
- Make sure your type is easy to read.
- Use subtle shading and color.
- Avoid mixing and matching too many font types and sizes.
- Align items properly.
- Consider how your app is used.
- Use appropiate typefaces.
- Add physicality and realism (if appropriate).
- Create engaging artwork.
- Heave a beautiful app icon.
- Make your app useful, intuitive, and beautiful.
- Read the iOS HIG (Human Interface Guidelines).
- Don't sacrifice quality for anything (graphics, typography, performance, ...).
All of these tips are extracted from iPhone and iPad User Interface Design video from the iOS Development Videos on the iTunes U.