Spend time on your business plan. How big is your market? How much value are you delivering? How much will people pay? What will you have to spend to make a sale? Could you support your app with adds? Do you need a free and a paid version?

Then, find someone who is at least conversant in your market area, and spend time on your product. What does it do for me? What is the most basic feature set you can ship it with? What is the most important feature? The second most important feature? Write down all the features on note cards. Sort by value. Why are those things at the bottom even there? These discussions should be a back and forth. Lobby for your feelings but come to a consensus. You're already half blind to the needs of user.

Now, you have to chose between hiring a consulting firm vs hiring individual developers. I work for a consulting firm that does mobile and web applications, so I'm a little biased, but I've worked as a developer on a distributed team being hired individually off craigslist. In the end, the consulting firm should be able to eliminate (or at least reduce) the amount of technical risk. People that have done this before, do it every day, and can show you their previous projects that are similar to yours can give you a very good idea of what it will take to get your app going. Individual developers will be cheaper to hire, but will be much more difficult to judge.

Next, throw out to specifications. Write user stories that break down your features into a deliverable unit of work that you as the customer and as the user can verify works. "It has a log in system" -- no. "A user can log in" -- yes. "A user can log out" -- yes - and this can probably be done later in the development cycle, and no VC or demo watcher cares that you can log out.

Go to meet ups. Tell people about your idea. Don't make them sign NDA's, get them excited. There are no ideas that are so good that if you tell it to people they will instantly give up their idea and start working on yours. None. You're going to have to spend hours convincing them that your idea is better, and to come join you and make it work. Starting to get this speech down right now is better than waiting till you've got an audience with someone you really care about.

Resources
http://www.pivotallabs.com/ <- Where I work
http://www.pivotaltracker.com/ <-- How to manage the software development right
http://www.softwarereality.com/soapbox/nda.jsp <-- NDAs
http://steveblank.com/ <-- Minimum viable product