I just found out that someone on my staff is looking for a new job. Should I let him know I'm aware of his job-seeking efforts? After all, how can I make long-term project plans that include him when I know that he plans to leave the company?

There's an old saying that applies here: Silence is golden. Looking for a new job is a normal behavior that most employees engage in periodically to test the waters for other opportunities. Job searching gives them a chance to let off some steam while they often discover the grass is actually more verdant on their side. If you tell him you know he's job hunting, however, that could ignite an uncomfortable atmosphere that actually encourages him to leave. He might even come to resent you if he feels you know he wants out, but aren't doing enough (in his mind) to keep him on board.

There's another popular adage that applies here as well: Be prepared. Even if he has no serious intentions of jumping ship, you shouldn't be planning long-term projects that hinge solely on him - or any employee - according to the Boy Scouts' motto. You have to assume some staffers might bolt to another job, take sick, or be otherwise unavailable at any given time. That's why you should always have a plan B in place to account for such unexpected interruptions. By preparing for the worst, you'll always function at your best, with little chance of staff attrition disrupting the quality of your marketing program.