What is `Organisational Culture`?

Organizational Culture as Defined by Schein
Robert Chenault
Schein describes organization culture as "a pattern of shared basic assumptions that the group learned as it solved its problems of external adaptation and internal integration, that has worked well enough to be considered valid and, therefore, to be taught to new members as the correct way you perceive, think, and feel in relation to those problems. Cultural norms are often referred to as, "the way we do things around here."
In terms of changing culture, efforts should be directed at creating norms that allow for individual preference while supporting the desired behavior.
One of the biggest challenges in successful cultural change is to identify key behaviors that are critical for organizational success. The cultural change effort should then be directed at making that behavior a norm.

Mindset versus Culture
Ronald Liebman
Trice & Beyer's discussion is excellent, but much of what others pass off as "culture change" these days is not. Rather, it is more often just shifts in espoused values (see Schein). We should not conflate tactics with strategies. (Even T & B were somewhat guilty of this).
True culture change is more often generational than not. If people's most basic cultural assumptions and references are treated as relatively fixed (but not necessarily alike -- see Haidt), we might redefine a quality culture as one that continually expands an organization's value to its customers by giving expression to the values of its employees.
This turns the problem around and yields a different -- but in some ways more interesting -- set of solutions.

ABC: Attitude, Behavior and Culture
Kouwenhoven
We define Culture as the collective Attitude and Behavior in an organization.
In any organizational change initiative (project/programme) we define the 'new' desired behavior. Not by imposing more rules. We engage all stakeholders and focus on the underlying attitude which leads towards the behavior. We create awareness on the attitude by looking at and addressing the behavior. So by engaging all stakeholders and by rewarding the 'new' desired behavior.
The people involved in time (6 months) change their organizational culture.