There's lots of information--much of it conflicting--about what it takes to be a great boss. You need empathy, or the ability to see the big picture. Or maybe you need to learn to understand and value different types of employees. But there's one simple thing all effective bosses absolutely must do--and so does everyone else. Unfortunately most of us--very much including me--aren't very good at it at all. Most of us are bad at saying no.

If you're like most people you can easily come up with several instances in which agreeing to something when you really didn't want to caused you frustration, overwork, financial loss, or heartache. If you're running a business or leading a team, it can also cost you opportunities, because saying yes to a bad deal now will often prevent you from making a better deal later on. This is why some of the smartest people I know say that their successful careers resulted from the things they said no to.

Beyond all that, being able to turn people down firmly yet kindly is an essential skill for every boss. But what if (like me) you find it dreadfully difficult to say no to anyone about anything? Perhaps (again like me) you've built a successful career on being a can-do person who always says yes to everything and then manages to get it all done. But now you've arrived at the point when you need to set better boundaries in order to reach the next level in your career. How do you go from being an always-yes person to a sometimes-no one?

Here's how to start:

1. Use a delaying tactic.

In many cases, you don't really need to say yes or no to a request right away. So, when someone asks you for something and you're not sure you should say yes, practice saying this sentence: "Let me think about it and get back to you." 

The very next thing you should say after that is when you will get back to them. "I'll give you my answer in 24 hours. Does that work for you?" It could be two hours or one week, depending on the urgency of the question and whether others will be inconvenienced while waiting for your answer. What if someone insists they need an immediate answer? That's usually a good reason to say no.

Now that you've bought yourself a little time, use it to think about why you're reluctant to say yes, and whether there would be negative consequences to saying no. Also think about how you could use the time or other resources you'd save if you say no to the request, and then make a decision. You should, of course, keep your commitment to provide an answer when you said you would. 

2. Make sure to preserve the relationship.

Look for ways to let others know that, even though you're saying no, you care about them and their concerns. This might take the form of suggesting someone else they should ask, or offering some other form of assistance. Make sure whatever you offer is easy for you to provide, though. Otherwise, you might just as well say yes to the original request.

Even if you can't offer alternate assistance, take the time to let the other person know why you have to say know, and that you really wish you could help them.

3. Practice.

If you're like me, saying no means stepping outside your comfort zone, and as always, the more often you do it, the less of a struggle it will be. So practice saying no, especially when the stakes are low. No you won't go to the movies with your friend (unless it's a movie you want to see). No you won't cook for your family get-together--they can order pizzas instead.

Get a few harmless nos under your belt, and when a customer wants you to take on one more project than you can reasonably handle, or an employee asks for a job he or she isn't ready for, you'll be better prepared to say no gracefully and without too much angst. You may even discover that whatever you say no to isn't such a big deal after all.