Next, we should go about designing a wire frame mock up of how we anticipate interacting with our application, so that we know exactly what we are looking for in our prototype. The following screenshot shows how a wire frame should give a visual representation of how the user will flow through the final application. In the quick wire frame of a dictionary application below, we gain a good idea as to how the user will interact with our work.

Often, it's useful if large sketch paper is used when designing an interface. This allows space for notes and multiple screens to be sketched.

We'll be designing an application in either landscape or portrait view, and may want to place out multiple possible screens on our page of sketch paper to help lay out an intended application flow.

From here, we can begin to sketch out our interface on screen. Buttons, text, and other interface elements can be placed in the approximate size and position that we desire our future app to look like.

Take a quick note of the visual changes that occur when a finger is placed upon the interface. Does touching a button cause the user to place their hand over important data? Do buttons seem to be spaced far enough apart that a user could easily tap on one without errantly tapping upon another?

Ideally, we will go through three or four revisions until we design something that we could see ourselves enjoying on our iOS device.