The use of the iOS is one of the latest technology toys available. With the basic code available to be downloaded and fiddled with more and more people are using it to design applications. Apple actually encourages this for their iOS for the iPad, iPhone, etc. and there are guidelines set up on their website for how to go about it. Having a good idea is the main thing, and once you have this you need a bit of know how and then follow the guidelines before you can present it to them for review.
The need for sticking to the guidelines is pretty obvious as they can’t have every Tom, Mary or Patrick designing stuff all over the place and expecting it to work on their system’s iOS. There obviously has to be cohesion between all the applications and the main business.
Photoshop has help in the form UI, and then you need to design in the same form as you do for the web just in a smaller fashion. With iPhone, it’s a good idea to start by examining some graphics that are already in use and examine how they are put together. Apple gives you some common tools that are used in their applications and most of these needs to be included in your design. You will find them in the interface of the builder or in the UI kit. Using Photoshop is recommended as the iPhone gives various documents, which will include some graphic templates, which include actual iphone sizes.
I tend to use my own sketches which I do freehand as the basis of my designs in the application. I then transfer these into Photoshop and make these correctly sized for the application. Obviously, you will need a series of drawings, and these will be the basis of your application.
If you don’t want to use your artistic abilities but want to start right into the application you can download for free from Teehanlax.
This is a UI kit which you can use as well as documentation. This can be used as the basis of your design. What I would do is keep the original and make a copy to use to make your design. This way you don’t have to re-download again and again but have an original you can copy again.
Give yourself different directories so you have separate views for each stage of the design. Because they are for iPad or iPhone they will be saved in the form of psd, but it’s also important to save them as .pngs or jpgs. This means that people who don’t use photoshop can also work on them.
You can get wireframes especially for iPads and iPhone from Graffletopia.
This is very useful, especially when starting out on this road. For an example of how many people find this useful more than 41000 downloads have been made from this site.
iPad has its own Gui Kit, and this is available for download.
They say you can make your own application in 30 seconds which personally I doubt.