When choosing a Unique Selling Point or Brand Position it is easy to think "What makes my product or service different?" and then take that as your position. 

Better though is a marketing-led approach. Identify a position that is unique and do two things:

1. say you have the best gizmo in that domain.

2. focus relentlessly on making your gizmo the best by doing it more than anyone else. 

If you have chosen a unique position then, assuming a reasonable level of compentence, you will quickly have the best gizmo in that domain. i.e. become expert by only doing one thing again and again. Then you become the best and you have a virtuous circle...

See the excellent Volvo point below (from a very good article).