When I worked for R.R. Donnelley there was a huge mission statement poster hanging on the wall by the door to the bindery. I walked by it every working day for almost 17 years.

The fact I can't remember anything about it other than that it existed tells you all you need to know.

Most mission statements are like that. Well intentioned? Sure. Intended to set direction? Absolutely.

Waste of time? Sadly, most of the time.

Here's one that's not.

That could be because the deck is the result of over 200 hours of work (including thinking and discussion time) by Dharmesh Shah, the co-founder and CTO of HubSpot, the inbound marketing company that has gone from $2 million in revenue in 2008 to over $50 million in 2012, placing it at #314 on the Inc. 500.

"In the early years of HubSpot we didn't talk about culture at all," Shah says. "A couple of years ago I started a simple document that talked a bit about culture, describing the kinds of people that seemed to do well at HubSpot and that we wanted to recruit. Then I started getting feedback from the team that it wasn't going far enough: It described the who but didn't address any of the how or why."

So he decided to go farther--a lot farther. Here's Shah on why feels all the time and effort was worth it:

1. Culture improves decision-making.

Culture helps make a large body of small decisions quicker--and a small body of large decisions easier.

2. Product is to marketing as culture is to recruiting.

Just like attracting customers is much easier with a great product, attracting amazing people is much easier with a great culture. The goal is to create a culture that appeals to the rights kinds of people and gets them to self-select.

3. The interest on culture debt is really high.

Culture debt is when you take a shortcut and hire people because they have the skills you need and you're "hurting" for people... but they're not a good culture fit. You let the "culture bar" down. When you bring on people that aren't a fit they infect other parts of the organization; even after a culture misfit moves on, their corrosive effects on the company live on.

4. You're going to have a culture anyway.

You can and should influence it--so why not build the one you love?

So where should you start if you want to create a mission statement that actually means something--and that helps you run your business by establishing and codifying goals, practices, and principles you both follow and measure?

"A common question I get from my start-up friends," Shah says, "is how much time they should spend on culture given everything else going on (like building a business.) I'm not sure what the optimal number is, but I can say with confidence that the number is not zero.

"I'd suggest 20 hours," he says. "Just enough time to think about it, talk to your team, read some stuff, and describe it. You don't need to put posters up on the wall. Just something--even if it's a one-pager that captures your current thinking on the kind of company you want to be.

"Quick hint:  You want to build a company that you love working for.  The rest will work itself out."

Note: If you're interested in how Dharmesh feels HubSpot "walks the talk" of its culture code, check out this post where he candidly grades the company's current performance against its 10 key tenets.