I could talk about building a team of the best talent you possibly can around you, or the importance of being the best leader you can, because, if people are clear in their objectives and are motivated to reach them, you've already significantly increased your chances of success.
However, I think the single biggest impact on success is knowing your business. The people who know more about their consumers than anyone else and their own business - by which I mean your share, profit and loss, marketing efficiencies and so on - than anyone else, will ultimately win in the market. It makes total sense to me that this knowledge enables you to make the right decisions more often, each one with a higher likelihood of success than the guy down the road who's shooting slightly more blindly. My advice: know your numbers.