If you do a car shop that requires an appraisal always always always always use a cheap backup key that you don't mind leaving and DO NOT GIVE THEM YOUR KEYRING.
I had to threaten to call 911 and report my car stolen once. I had my phone out and had dialed the 911 and he stopped me before I hit call and STILL tried to talk to me before getting them.
Not only are car shops a huge time eater, but then they keep calling, and sending post cards, and (I'm sure of it) selling my info to junkmailers. No, I'd rather poke my eye out....