Effectiveness Tip of the Week via the folks at FranklinCovey:
First, some Quotes:

• "Learn to say no. It will be of far more use to you than to be able to read Latin." -- Charles Haddon Spurgeon
• "A 'no' uttered from the deepest conviction is better than a 'yes' merely uttered to please, or what is worse, to avoid trouble." -- Mahatma Ghandi
• "When your daily activities are in concert with your highest priorities, you have a credible claim to inner peace." -- Hyrum Smith

No Thank You

No. Nicht. Nulle. No matter how it comes out, saying "no" isn't always easy. Project overload, interruptions, and demanding coworkers can make it tough to speak this language. Remember, you have a right to say no... graciously but firmly. If you respond evasively, you'll build false expectations. Saying no takes practice. Here are some phrases that might help:

• "I have so much on my plate now that I don't know when I can get to it. But I do know someone over here who can help you now."
• "Sure, I can help you with your request as long as we both understand that what I agreed to do for you yesterday might be delayed."
• "Thanks for thinking about me, but no thanks."
• "I won't be able to do it until tomorrow, but I could provide you with some resources that might help you do it today."