Do your homework (market research) to make sure your product / service (solution) solves a market need and you are competitive versus the completion.
You have clear long, medium and short term goals with action plans.
Have somebody you trust to discuss the business when things get challenging, because they will.
Read as many books as possible on successful and failed ventures and related material! so much to learn and helps keep up the motivation.
This is a brief list of my favorites so far: (please share yours!)
The intelligent entrepreneur
The Lean Startup
Grit the passion for success