"Intrapreneurship" can keep your job and your company interesting and competitive, but it comes with its fair share of obstacles. How to pitch your idea to the powers that be.

By Anne Fisher, contributor

FORTUNE -- Dear Annie: I have an idea for what I think would be a terrific new line of business for the company I work for, but I'm daunted by the thought of actually trying to get it off the ground. Senior managers here sometimes talk about encouraging people to be more "intrepreneurial," but this isn't really a startup-incubator type of culture like, for instance, Google. (Most of our businesses, which are widely diversified, are in old-line manufacturing and transportation.) I need to figure out the best way to approach higher-ups about getting support, including funding and staffing, for my idea. Can you or your readers give me any pointers? — All Fired Up

Dear AFU: As you probably know, intrapreneurship has a long and storied history in U.S. companies, going back to the famous "skunk works" at Lockheed Martin (LMT) during World War Two. A more recent example is Apple's (AAPL) Macintosh, which was developed by a small, informal team led by Steve Jobs, who later described the project as "a group of people going, in essence, back to the garage, but in a large company."

"Innovation in companies doesn't happen without intrapreneurs," says Gifford Pinchot. "Almost every big, game-changing invention you can name is the result of a passionate person pushing it through despite others' efforts to kill it."

Pinchot, a Seattle consultant who founded and runs a business school called the Bainbridge Graduate Institute, is generally credited with having coined the term "intrapreneur." He wrote two books you might want to check out: Intrapreneuring: Why You Don't Have to Leave the Corporation to Become an Entrepreneur and Intrapreneuring in Action: A Handbook for Business Innovation. Take a look, too, at Pinchot's web site, which features 10 Commandments for Intrapreneurs.

Commandment No. 1 may give you pause: "Come to work every day willing to be fired." Gulp. Trying to launch a new business within a huge bureaucracy isn't for the faint of heart, in part because, Pinchot says, it "triggers the corporate immune system," inviting resistance from people who see any change to the status quo as a threat. (In your own company, I suspect you know who these people are or you wouldn't be, as you say, "daunted.")

Based on his own experience (he once started a new consulting business within a large firm), and that of hundreds of other intrapreneurs he has interviewed and studied, Pinchot suggests three ways to start turning your idea into a reality: More