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:  1. Find an influential sponsor. “These days, there is less money around for trying out new lines of business, because so many companies are in cost-cutting mode,” Pinchot notes. “But there is always a way to get resources for the right project.” Begin by persuading one higher-up that your idea can fly — maybe one of those senior managers you mention who talks about encouraging intrapreneurship. Says Pinchot, “Friends in high places can calm the corporate immune system for you” and champion your cause.  2. Connect what you’re proposing to what the company is already doing. Rather than pitch your idea as a radical new concept (even if it is one), Pinchot advises describing it as “a logical extension of one of the company’s current businesses. Too much change too fast scares the hell out of people, so avoid overdramatizing or overpromising. Emphasize that you are just exploring the idea and testing it with potential customers, which is always a sound strategy anyway.”  3. Begin with small requests. “The trick in the very early stages is to always ask questions to which the answer will be ‘yes,’” says Pinchot. “Take small steps. Get people used to saying ‘yes’ to you.” For instance, instead of asking to have someone assigned to help you develop your new business, be ready to do the lion’s share of the work yourself. “Asking for the moon right away” will just stir up naysayers, Pinchot says: “You don’t want to give people a reason to attack what you’re doing.”  To that advice, Mike Kestenbaum adds a couple more tips. A former investment banker who joined giant Internet company IAC IACI in 2004 as a mergers-and-acquisitions analyst (he helped IAC acquire Dictionary.com and CollegeHumor Media), Kestenbaum now runs a new IAC app he invented, CrowdedRoom.com.  “Do your homework and know the market — especially the potential customer base, and the competition — inside out,” he says. Overcoming skepticism about your idea requires that “you know more about the market for it than anyone else in the room.”  Kestenbaum also recommends “tapping into the skills of other people in your company. I was lucky in that IAC has so many people who are experts at making new sites successful,” he says. “You can also get input from your in-house specialists in new product development, market research, or wherever your own skills aren’t quite enough.”  Pinchot couldn’t agree more, partly for an interesting political reason. “Asking for advice is a good way to get people on your side,” he says. “So ask, and then be sure to thank them for their insights.” This is especially helpful, he adds, if you can enlist the expertise of someone who is trying to block your idea. “Once you have involved that person in your project, you engage their ego. They’re now contributing to it, so it must be good,” Pinchot says. Expressing your sincere appreciation is essential, he observes: “Very few people can resist gratitude.”  Talkback: Does your company encourage “intrapreneurship”? If you’ve ever proposed a new product or service, what became of your idea? Leave a comment below.
“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.