iPhone has really caught up the imagination of both developer as well as consumer community. If you know the skill of web-designing or you have experienced and innovative web designers working for you, then you can easily make inroads in consumer's mind space. If you have ideas and technical skill, then you can use the following steps and tips
1) have an idea and analyze it
Does you idea have a target audience? Does your application offer anything different to them, which other apps are not offering? Do you think your app will make their users loyal to your brand, or keep them loyal if you already have a loyal customer base? What all skills are required to make this app?
2) Make sure you have all tools required for building iphone app
Join Apple iphone developer program. It will cost you $99 and you will also have to sign a non-disclosure agreement. Get the software development kit for developing the application, if the application is native. If you application is browser-based, then you need to install safari on your desktop. Make sure that you have downloaded guidelines given by Apple.
3) Understand what you are good at and research the market
Are you good in doing market research to understand the pulse of your target customer base? If not, then hire a good market analyst to help you on this front. Follow the same route for development and marketing of the application.
4) Make a storyboard, conceptualize it and finally make a design
Draw a sketch of what you application will look like, and how user will interact with the application. You need to give your imagination a particular shape. It will help your team in being on the same page with you. Use iPhone stencil kit for making a quick prototype.
5) Develop and Submit you application in app store, and promote it
Unless you are technically strong and have good programming skills, do not write the application yourself. Hire some developers for the same. Understand the technical feasibility from them, and see if you can afford it. Submit your application in Apple's app store. Join social media campaigns and experiment some more ideas to promote your application