Anticipate possible problems and downfalls of the business. Develop plan of attack when these things happen. Leave room for error especially with cash flow. Make sure can sustain business for 3 months with cash flow. Credit lines are great for this.
Prior planning helps anticipate future obstacles.
Research the market and competition. Underestimate revenues, overestimate expenses. If you don't know, ask for help. Focus on customer-the user of the product. If they are not interested, it's over.