Missions and core values are ubiquitous at companies today. They're expected — by employees, new recruits, even investors — because they take a stand on the company's purpose and path to get there.

You need both because one without the other isn't enough. A mission is the purpose of the company, its north star, its reason for existing, whereas core values are how you fulfill that purpose, the set of navigational tools in service to your mission that are more useful for immediate, near-term decisions. They're a code of conduct, a common language, guiding principles, shorthand for new employees, partners and outsiders to understand how your company operates.

But you can't establish both your mission and core values simultaneously. While a mission is often the inspiration for the company itself and can be simply declared as the destination, core values are trickier. To last, and to be effective, core values need to be an authentic reflection of your company, your people and your culture; core values take more self awareness on behalf of the company than a mission.

A question I often get from founders is how and when to introduce core values, specifically: How do you identify what matters to your company in a unique way, and when do you really know? How do you get employees to understand, embrace and act according to these values? And, do you have to keep the same values forever? Here are five pieces of advice for establishing core values at a startup, or even revisiting values at a young and growing company:

1. Wait, Watch and Learn.

Companies are living entities full of forces, personalities, pressures and motivators. Just like people and relationships, the combination of these things produces something unique that drives it forward — and that something takes time to emerge. Even if you have a pretty good idea of who you are already, I always advise founders to wait to formally establish your values until you reach five to 10 employees and the company has been formed for a few months, but is still a couple months ahead of your first product launch. Observe how you make decisions together amid your different forces and personalities at play; this is probably the strongest signal of what your culture authentically is at its core (hence, "core values"). You can always make your values partly aspirational, but to make them stick you must also root them in reality.

2. Tie Your Values to Your Product.

Since core values are a guide to your every day, it's incredibly helpful if they tie to what you're building every day. The best example I have for this is from Zillow, where a core value is Turn on the Lights. Zillow was the company that brought real estate information out of the dark and into the light for consumers. While this innovation has now become an expectation among consumers, the core value of Turn on the Lights continues to keep empowerment front and center as the company matures and evolves. So at Zillow, the core value "Turn On The Lights" means that people are meant to be transparent with each other internally, but also that the product is supposed to provide real estate transparency to its users.

A more recent example is from my latest startup, Pacaso, where we have the value of "Empty the dishwasher: When you encounter an unmet need, step up and own it." Pacaso's service creates fractional vacation home ownership — in other words, owning a quarter of a second home rather than the whole thing, making it more affordable, accessible and practical for many more people. The core value of "Empty the Dishwasher" means that no job is beneath any individual employee. But it is also a nod to the product itself, since "emptying the dishwasher" is the ultimate act of teamwork inside one's household.

3. Be Prescriptive and Memorable.

Try to avoid corporate jargon and overarching words that are meaningless without context. In gathering my thoughts for this piece, I came across an article in Harvard Business Review and learned that the values "communication", "respect", "integrity" and "excellence" were all values of Enron — a company that committed one of the biggest accounting frauds in history. Clearly these words weren't prescriptive or memorable enough to keep the company on the right path.

If integrity is a core value, define what you mean by integrity, and make it something you'd say every day. My favorite example is from Box: "Make Mom Proud." This value is all about creating an environment of safety and trust where people's voices are heard and employees do right by one another. It's not corporate speak; it's pithy, playful and a clear reflection of their culture while also saying something specific about the way employees collaborate at Box.

4. Tie Core Values into Your Operations.

To truly live your core values, they need to be part of your existence at the company; you can't just print them on a poster and expect them to be followed. Your values should be part of how people join, operate within and sometimes exit your company.

Interview and evaluate candidates based on your company's core values, and even better, create standard questions for your interviewers to ask based on your values. This not only reinforces what the company is looking for, it also helps fight unconscious bias. Structure employee recognition around your core values for awards and announcements. Evaluate employee performance — including annual reviews, feedback loops and compensation — around your core values. At Zillow, core values were equally rated to outcomes in our annual reviews, which means you couldn't be an all-star and a jerk and be rewarded for it.

5. Revisit Your Values, and Amend Them Accordingly.

Like the Constitution, you need to be able to amend your core values — infrequently, but regularly. Why? Because things change. You grow. You acquire companies that have their own values. You evolve your business model. At Zillow, changes like these prompted changes in our values. When we acquired Trulia, we added the value "Act with Integrity," which was a core value of theirs but not part of Zillow's, yet critically important as once-fierce competitors became colleagues with shared objectives. When we expanded into buying and selling homes with Zillow Offers, we added a value around operational rigor and excellence, since new factors like time on market and closing deals quickly became critically important to the success of the business. Yes, you are creating core values, but sometimes your core changes as you mature, and you must consciously account for that every few years.

Core Values are a critically important part of a well-run company. But, like so many aspects of a company's culture, to make core values truly come alive takes effort. When well executed, they can contribute immeasurably to your company's success.