I got ALOT of good advice, so narrowing it down to "the best" is hard...
I'm 3rd generation Lawdawg in my family... Grandpa once told me... "When you are working, you are getting paid, and you don't get paid to loose a fight."
Dad once told me, "When you are working and contacting people, be polite, be professional, but be prepared to have to kill anyone you contact."