1. “I can’t commit to this as I have other priorities at the moment.”
2. “Now’s not a good time as I’m in the middle of something. How about we reconnect at X time?”
3. “I’d love to do this, but …”
4. “Let me think about it first and I’ll get back to you.”
This is more like a “Maybe” than a straight out “No”.
If you’re not interested in what the person has to offer at all, don’t lead him/her on. Use methods #5, #6 or #7 which are definitive.
5. “This doesn’t meet my needs now but I’ll be sure to keep you in mind.”
6. “I’m not the best person to help on this. Why don’t you try X?”
7. “No, I can’t."
http://zenhabits.net/say-no/
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Spend some time thinking over any requests before answering, and see if there is a compromise available.
Answer people with a respectful no.
Speak in an even, calm manner.
Suggest an alternative to their request.
Stand your ground when you are challenged. Do not give in to anger, bullying or abusive behavior. You have a right to say no to any request that you are uncomfortable with. Say no, and mean it!
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Transfer ownership of your refusal to something else. For instance, say "I can, but my schedule is booked now. How about some other time?" You don't have to explain further. This deflects any resentment they might have towards your schedule.
Don't feel obligated to explain. You have your reasons and they may not be ones you wish to discuss. If this is the case, try saying something like, "I'm just not able to." Leave it at that - if you must, change the subject, or say, "I'm sorry, but I need to go."
Stand firm. If the requester does not want to accept your answer, tell him or her that your mind is made up and that you will not change it.
Do not lie when you explain why your answer is no.
http://www.wikihow.com/Say-No-Respectfully
