How to say "no" without being an asshole -- Lifehacker

http://lifehacker.com/5875337/how-to-say-no-without-being-an-asshole

First, don't be an asshole.

But sometimes a poorly phrased response might make you sound like an asshole even when you aren't.   Note: I just wrote the word "asshole" 4 or 5 times depending on how you count it.

I find the best way to say "no" in a positive way.  For example, instead of saying "No, I don't want to do it.", I say, "Yes, I would love to do it.  Let me check my schedule and get back to you."  This gives me time to make a decision.  If I want to do it, I get back and say "yes".  If not, I get back and say "No. I have a previous engagement."