"At one time or another, most of us have avoided saying no by saying yes," writes Rick Brenner of Chaco Canyon Consulting. "We do this in spite of our experience that the price we pay for agreeing to do something we don't believe in is often far too high." Here are some suggestions from Brenner on how to say no when you need to:
"I don't know how to do that." This is Brenner's recommended starting point, assuming that it's true—which often it is. (Of course, if somebody's asking you to do something that's wrong, stupid or unethical, it's probably much easier for you to say no without hesitation or guilt.) "If someone has asked you to do something, and you honestly don't see how you can get it done, say so," he writes. "It's better to let them know now than it is to have them discover it later."
"Can you help me?" This is the obvious next step when your real problem is that you don't know how to do what's being asked within the constraints you face. Be specific about what those constraints are and how they could be eliminated. Do you need more time? Do you need other work to be put off in the meantime? Do you need more resources or changes to be made elsewhere in the project or the enterprise? Asking and answering these questions turns saying no into an occasion for needed problem-solving.
"It's possible, but ..." If you sincerely don't think there is anything that can be done to ease those constraints, one way of saying so is a "can-do" approach. For example, "We could do that. It would take more time and resources, but we could do it." Another way is to highlight the odds for or against success—"It's possible we could do that, but unlikely. I'd say the probability is less than 10 percent." Of course, your team members, colleagues or superiors may just hear the "it's possible" part and not the "unlikely" part. But it's nonetheless better to demonstrate that you're open to the possibility of success than to simply say "We can't do that." It will also, probably, feel better to you when you're saying it.
And it's important that you feel OK about saying no if you hope to be succesful at it. "To feel good about saying no, start by feeling good about yourself," Brenner writes. "Then adding the no is a small step. When you say no, you're just stating the truth as you see it."