Focus on your customer. A lot of start up business owners my self included like to think about your product and/or service. That is probably the part of your business that you are most passionate about. In my view, the way that you actually make a business succeed is start with your customer. Who are you going to sell to? What are you going to sell? Why would they care? If you can get those first few customers and actually make a sale then you are on your way. Try and resist focusing on your product and service in advance of having any customers.