There is the old adage that if you build it, they will come.
So you spend time and money building out your product or service offering and then you open the doors expecting a flood of customers - but there are few if any.
There are two key problems with the build it and they will come principle:
You must seek feedback from your ideal customers on what they think of your business proposition and how much they are willing to pay. Even if you have to stick together a mock-up with sticky-back tape and cardboard!
Just find out what people think (not just your ma & pa and girlfriend who all love you very much :) You need feedback from those who will give you honest feedback - warts and all).
There is the well-told story of Tim Ferriss who tested the title for his genre-defining book, 'The Four Hour Workweek' against other potential titles (there was one preferred to TFHWW) using Google Adwords. He simply counted the clicks. Eh voila!
So even if you have a great product or service (that's been validated through advance feedback ;)) the risk is that, unless you have very deep-advertising-pockets, no-one will find you...
Here you have to get strategic. You need to know who your ideal customers are and you should go hang out where they hang out (both digitally and physically). Think forums, blogs, trade associations, exhibitions, conventions, podcasts, speaking gigs. For those with deeper pockets, there are online paid ads e.g. Facebook, Google ads etc. And of course, there is the good old phone and snail-mail (remember, this must be highly targeted).
So don't assume that just because you have the whizziest product or service that customers will be beating down your door. It rarely works like that.
The above points could save you a lot of frustration, stress and....cash!