1) Make sure you are adressing a real problem/opportunity, which is important enough for people to care about it and invest (time/money/etc) in a solution for it, big enough (could be measured in different ways - users, businesses, money, etc) for you to care about, and hard enough to solve to allow you to differentiate your solution (best if the product itself is differentiated, but could also be execution, partnerships that you have, etc). It's critical that the above is well articulated as your mission statement, and that if asked - all leaders in your company will be able to say it.
2) Have a clear strategy and roadmap you can always check against and ensure that your current assumptions still hold and that your current execution still follow it. Strategy sang roadmap can be at a high level, and it's fine not to follow it (I.e in a fast moving market), but I think it's critical that you do it consciously, and not going down some slippery slope.
3) The people you hire and execution. I think that these are by far are the most important, since many successful companies pivot / expand their strategy and product. It's actually their ability to do so is what makes them successful in the long run imho. But getting these two right is easier said than done. It requires the company to have a corporate DNA with values that are dominant in every function and aspect (from the hiring criteria, through the office design, rewarding and promotion system, internal and external communication style and policy, product design principles, red tape and hierarchy, etc). Values/principles which I think are critical are: data and measurablity at the core of every goal and decision, innovation (nailing this one right is a topic by itself and touches sharing/open culture, ability to experiment and fail/learn quickly, effective communication channels, the red tape and hierarchy angle, etc).
i will finally :) end with a short point on the most important point there - the team you hired. Have a thought through hiring process, and never compromise on your hiring bar. A good team makes everything possible, and it's better to not yet have the right person with you, than to have the wrong one.