If the customer/user doesn't understand: it's your fault, not their problem

I remember, a few years ago, a client was in the office of the company I was working for at the time and they were showing off the promotional flyers they'd printed and were busy distributing to potential customers.

After they'd handed us copies they remarked that the people they were trying to reach just "didn't get it". They were handing out all this information about how clever the technicalities of the system were and all the things it would now enable them to do but everyone they spoke to just asked about price (which wasn't mentioned on the flyer).
As far as their potential users were concerned, all they were interested in was price. All the other whizz-bang features were of no interest to them. The company in question had wasted a lot of time money and effort in trying to tell people about what they were offering but it wasn’t anything their potential customers were interested in.

So what does this have to do with building phone apps?

I think it demonstrates two areas where app developers often make mistakes. They build an app without understanding their desired and potential market and they don't make their value proposition clear. 

Understand your market

If you're not making something people want or that is different from an alternative in a way that is “better” from the users perspective, you’ll find making sales hard.

This means:
- thinking before building an app
- building something that there is a market for. (Yes, this means going and doing some research first.)
- not just building it because you can or it's technically possible

It’s easier to sell something if you build what people want than it is to build what you want and then try and persuade people to buy it.

Make your value proposition clear

Explain what your application does and how that will help, benefit and provide value to the user. This will enable them to make an informed decision about purchasing the application and ultimately encourage them to do so.
Of course, this may mean that you have to explain what the application cannot do. Whether this is through decision or technical limitation. By making this clearer before they have the app and are trying to get it to do something it can't you'll make them happier. No, not everyone will read a long description about the capabilities and limitations of the app so you'll need to be smart about how you communicate this.

I think no customer is better than a disappointed one who is complaining and spreading negative word of mouth. Focus on getting the ones you want and the ones who want your app. It'll make everyone happier in the long run.

At the end of the day it comes down to building what will sell and communicating (marketing) clearly. Do this and you'll have more success with your apps.