I ran across Merlin Mann's talk about How to Fix Meetings. It's good, if a little long, so if you're interested in the topic, check it out. But there's one jewel of an idea that I found there that I wanted to call out:
"We aren't dumb. People chase Big Dogs"
This is an invaluable lesson when analyzing your own corporate culture. Forget the mission statements, the surveys, and the focus groups. A "culture" at an organization is the collection of unwritten rules that people either follow, or risk some level of ostracism when they don't. They are usually hard to define, and almost never written down or formalized (mostly because of how very difficult it is to pin them down, particularly from *the inside* of the organization).
But no matter what organization you're talking about, its culture can be discovered by asking "What do people see *as succeeding*". What works? What doesn't? Period. People follow the Big Dogs.
"Big Dogs" doesn't mean management, either. It means those successful people in whatever corner of the organization that are generally understood to be effective. It's about what those people do (not what they or their managers say) that we pick up on and emulate.
When you've identified the Big Dogs, and identified what they do to be successful at your organization, it's pretty easy to identify the culture.
The hard part is determining whether or not the culture you have is the culture you want.