Marketing isn't just about advertising. It's also about building a product that lots of people want (or that some people want a lot). If you're a programmer who's serious about making money from your Windows Phone 7 applications, you might despair to learn that to do your development effort justice, you need to spend almost as much time on promotion and polish as you've spent coding. There are two things you need to do in order to get sales:
Do your market research (show your app to some friends) and try to get inside the head of your customer. Most smartphone app sales are driven by word-of-mouth and website reviews, so the best way you can sell more copies is to have a better product.
There's no point trying to sell an application on the Windows Phone 7 Marketplace if the kinds of people who would want your application don't use Windows Phone devices. Don't feel guilty about making sweeping generalizations; it pays to think about what kinds of people have Windows Phone 7 phones and target those people.
Microsoft has a clear idea of what kinds of people it wants to buy its phones. Microsoft calls these folks “life maximizers,” and this target audience has the following characteristics: