What to Do: “Let him know that this is strictly voluntary,” says etiquette consultant Jacqueline Whitmore. If it’s a big project that will require after-hours work for more than a week or two, offer him an incentive, such as tickets to a ball game. Then, when he does help, send an e-mail to his manager telling her what a great team player Joe has been and copy Joe on it.

What Not to Do: Don’t go behind his back to ask his supervisor — check with him first.

Sample Script: “I really need your expertise on this project. You’d be helping me out a lot, and I want to make it worth your while. How about tickets to the Yankees–Red Sox game?”