Project Management Glossary
The issue of support from people outside your direct control is a common one. Most projects are staffed by people from several areas of the organization, rarely do they report (in the traditional sense) to the project manager. They are, in effect, "borrowed" resources and they're usually "borrowed" from someone who already had plans for them.
One way to build support is to carefully connect the goal of your project to larger goals in the organization. You should be able to show how achieving your project goal will further the goals of your own area. Try to develop the same connection between the project goal and the goals of those managers from whom you need support.
The farther up the organizational chain you can draw this line, the better. Start with your work group. Move on to your department. Then to your division, etc. Try to pick up the necessary managers along the way.
Depending on the project, you might try looking for goals that involve such things as interdepartmental cooperation; customer service improvements; productivity improvements; divisional revenue enhancements; new product introductions, etc. The tighter the connection, the stronger your case for the support. Using higher-level, longer-term goals as the basis for your request can frequently overcome short-term objections.