The Kauffman Foundation conducted a survey of entrepreneurs. The findings can be inferred from the table of contents.
Experience, Management, and Luck: The Keys to Success
Professional Networks, Education, Funding, Personal Networks: Important
Location, Investor Advice, Alumni Networks, and Regional Assistance: Not so Important
Entrepreneurs Perceive Very Few Obstacles for Themselves.
Entrepreneurs Believe Entrepreneurship is Very Risky and is Hard Work
Using Personal Savings is the Norm, Venture Capital Comes to the Experienced, and Friends and Family are Always There
Other Success Factors
Entrepreneurship is Believed To Be Stressful, With Unanticipated Challenges
As an issue of methodology, the survey is assuming that entrepreneurs are correct in their perceptions of the sources of their success. Self-deception and the lack of a control group could be problems.
I personally would emphasize a desire to sell. If you cannot overcome your fears and insecurities about selling (and who doesn't have those fears and insecurities?), then you are very unlikely to be successful. The notion that you can have such a great idea that it will sell itself (or "go viral," as they say) is very seductive and in my view almost always wrong.
From Poverty to Prosperity turned out to have a big focus on entrepreneurialism, in part because of interviews with Edmund Phelps, Amar Bhide, and William Baumol. I created a list of entrepreneurial temperaments and found that when I reversed them--creating an "anti-entrepreneur"--the resulting personality is in fact a typical bureaucrat, colorless and rigid.