Culture is defined as the shared experiences, knowledge, norms, and language between a group of people. That group of people can be an organization, a team, a family, or even a society. For today's analysis I'll think of culture from a startup perspective.
There is no inherent right or wrong culture. Every startup has their own unique ways of being, forged through time and practicality. Thus, though there are best practices in building culture, those best practices are at best suggestive, not prescriptive.
Culture morphs through time and mass. As you develop over time or have more people, your culture should change. If it doesn't something is wrong and you're likely hanging on to something in the past.
Culture is composed of the daily stuff and the big stuff. The daily stuff reinforces certain behaviors and makes culture consistent. The big stuff are the life changing events; things that question one's own existence. The big stuff pulls people together and changes culture in a big way. The key is to turn those things into positive, learning experiences.
I think that's how culture is built - through the big things and reinforcement through the daily things. The big things swing the culture one way or the other way. The small things reinforce those learnings; like someone once said - culture isn't what you say, it's what you tolerate.
Culture is helped by a strong founder who has a well defined view on the world. That may be a wrong view and subsequently the wrong culture, but that is exponentially better than having no view or no culture. A strong culture allows momentum and a team to grow, and no culture doesn't allow any of this.
A strong culture is hard to define and quantify. Sometimes it's artifacts like physical office, books, etc. Sometimes it just feels different. I have yet to know how define it and even value the impact it has.
But not knowing how to value it doesn't detract from how important I think it is. Good culture makes people responsive and productive. Good culture scales to different teams and geographies. Good culture can recruit people that you didn't think you could recruit. Good culture is the social glue, the mission we all want in life.