First thing I started with was researching what my competition would be. Are there any other apps out there already providing the same service - in my area or out of it. There are a couple that I'm aware of Buddytruck & goshare. How successful are these companies? Are they competing in your market? How would you differentiate from them.
Second I would consider your supply chain - are there drivers with the right types of vehicles in the area? What businesses would promote your services to their customers? Engage with the business owners or executives to get their prelim feedback.
Third who are your target customers? How would you engage them?
Fourth would be your financial proposal. Is there enough potential revenue? Do you have the capital to finance it and keep it operational for a year? When do anticipate enough revenue to cover your costs...etc.

I'd be happy to talk through this with you and share my experiences and challenges particularly is founding my own tech startup.
Best wishes.
Allycen