Most of the time we always started with what do we want to do, what our products/services are. But the first thing we should think about is: what is the problem we'd like to solve. If no problem can be solved by our products then there will be no feasible business to do.
Once we have a problem to solve, then we can describe how do our products/services solve it. And to whom do we sell our products/services.
Goals are clear now. We now need to find out who is standing between customers and us. They are the barriers of our business. We must identify them to differentiate ourselves and create a unique selling point.
Finally, we should describe who are our team members, how much money we are going to spend and how long will we achieve our goals.