Small is big
The best way to own one's own big business is to start with a small one and make it bigger, and the best way to do that is to convince everyone that the small business is already a big business.
Bank managers
Trying to bluff a bank manager is a bit like trying to out-eat a Sumo-wrestler: it's theoretically possible but just not very likely.
Planning
The Business Plan must include a Budget. When it becomes clear that this is completely unrealistic, it can be updated by Forecasts, which in turn can be replaced by Revised Forecasts when they, too, prove to be inaccurate. It is absolutely vital that you are always able to point to an up-to-date plan which shows that the finances are on target (even if that plan was only produced the night before to formalize an existing situation).
The unexpected
The only things that are guaranteed to happen are those that could never be imagined (the First Law of Business Forecasting: expect the unexpected).
Good accountant
A good accountant should be defined as one who saves you in taxes almost as much as he charges in fees.