Everyone wants to know how to "change" their corporate culture to achieve the goals they want.  In some cases this means more risk taking.  In other cases it means more productivity.  In any case, corporate change happens in two ways:  external forces and internal behaviors.

An external force is usually not a good thing.  It means that something or someone has created a dramatic change that forces the organization to sit up and take notice.  This action could be a merger or acquisition, a significant shift in the competitive landscape or some other seismic change.  In these instances, the individuals within an organization are shocked out of their regular cultural attitudes and routines and often have a new culture or methodology imposed on them.

Behavior modelling is probably the most effective way to impact a culture from within.  While this sounds almost Freudian, the approach is very simple.  As Gandhi said, be the change you want to see in the world.  In other words, model the behaviors that you wish to see others display.  As an example:

In any firm, meeting attendance and timeliness are a cultural phenomenon, usually set by the management team.  If the most senior executive who attends a meeting is habitually late, then the team receives a signal that the executive does not value the meeting or timeliness.  This behavior is then copied throughout the rest of the organization.  If, however, the executive is prompt and expects prompt attendance, then the rest of the organization will model that behavior.  The same goes for using a PDA or Blackberry in a meeting.  If one person, no matter how senior or self-important, is allowed to regularly "check out" of a meeting to interact with their BlackBerry, then the precedent is set for everyone to copy.  Now, these examples have to do with modeling behavior around meetings, but ultimately the culture is defined by expectations and the behavior we as leaders exhibit in our daily work.

If you want to change your culture, change your behaviors and model the behavior that you want to achieve.