I always use a busy, public parking lot, but kind of removed from the main traffic portion so as to not cause alarm to nosy bizzy bodies who thrive on the 3 magic numbers...911.
I have used a parking lot at McDonalds, Walmart, Bob Evans, Golden Corral, and Lowes. I always meet in what I consider to be a good part of town, during daylight hours, and I always take a friend for back up. Plan ahead so you can park in a location where the security video is working, too. It helps to talk a bit in advance to the buyer. Learn enough about him to have confidence in him. Check out his INGO rating as a seller/buyer, and read through his posts. If anything makes you think twice, cancel the deal or arrange to meet in an LGS where you have made arrangements with the owner to serve as FFL. The FFL fee is well worth the extra security.
Late at night on a deserted highway on a dark, closed bridge.