What to wear to negotiate a good price on a used car?

Hi,

I'm planning to go look at a used car at a dealership tomorrow. I'm pretty sure I'll be making an offer on the car, but I want to make sure I can negotiate a good price on it. Any recommendations on what to wear? I have a pretty diverse arsenal of mones from different companies. Please see my signature below to see what I have available.

Thanks in advance for any advice you can offer!

PS The car is a Certified Pre-owned car and it's currently listed at $500 below Kelly Blue Book value, if that helps.