My personality is passive agressive. Stemming from that, I have always tried to be diplomatic. I'm very cautious in what words I choose when speaking, either in a large group or one on one because I don't want to offend anyone.
My own mother said I am a pharosie, though I know deep down inside what she really meant was I'm a savy diplomat.
Today I walked into a meeting where the top level execs of my organization sat around a conference table and I got to update them on what I have been doing for the last year. I had a few issues I wanted heard, but knew I couldn't blast them with my true feelings. I had to use words like "vigilant" instead of "over zealous retards".
As a result I defined for myself what diplomacy is. Diplomacy is cautiously taking someone up to the line without crossing it for the purpose of showing them what's on your side of the line, while keeping them comfortably positioned on their side of it. Then when you sense the first sign of discomfort, you pause for effect and back off gently to leave them feeling respected, yet aware of the issue.
Diplomacy is a key component of all aspects of life, but especially when negotiating. So when faced with negotiations in your organization, try my approach. It takes practice to get good at it and it's a bit of a chess game, but once mastered look out world. After being "diplomatic", I was told "This is the best report from your department we've ever heard."