Bellow is a summerization of apple HIG.
I will divide HIG to multiple parts. Following is part 1.

Display Size

Regardless of the iOS device, the following observation apply:

  • 44 X 44 points is the minimum acceptable size for a tappable area.
  • People are aware of the quality of the app.
  • app screen should be focused on content.

Difference between pixels and points

  • Pixel are used when designing the icon on an image application.
  • Points are related to the representation of views and icons on the iOS device

Notes

1 Point = 1 Pixel (non retina device) 1 Point = 2 Pixel (retina device)

Devices Sizes (in Points)

Device Resolution
iPhone 3G/3GS 320 X 480 points
iPhone 4/4S, iPod 4th 320 X 480 points
iPhone 5, iPod 5th 320 X 568 points
iPad 1/2 1024 X 768points
iPad 3/4 1024 X 768 points
iPad mini 1024 X 768 points

Devices Sizes (in Pixels)

Device Resolution
iPhone 3G/3GS 320 X 480 pixels
iPhone 4/4S, iPod 4th 640 X 960 pixels
iPhone 5, iPod 5th 640 X 1136 pixels
iPad 1/2 1024 X 768 pixels
iPad 3/4 2048 X 1572 pixels
iPad mini 1024 X 768 pixels

iOS devices and orientations

Launching an app on the iPad and the iPhone responds differently.

  • on iPhone app launch as Portrait by default
  • on the iPad apps launch as the current orientation of the device.

Preferences and settings

There is a difference between prefferences and settings.

  • Preferences are kept inside the application itself.
  • settings are kept inside the settings app.

Functional differences:

  • Preferences deals with user settings, such as accounts, notifications etc… (common).
  • settings deals with app general and global settings (rare to be used).

App help should be minimal

Reasons:

  • Tendency from users to disregard help
  • Tendency from users to dislike help
  • Help takes alot of space and time to be created