To cool off they say to wrap a cool wet towel around your neck Why?

Because there's a huge amount of blood flow through the neck so, the idea goes, cooling the cools all of you.. However, I don't think it works all that well, does it? The area you're cooling is really quite small, so there's not a lot of heat transfer. Instead, do what your body does: evaporation. Cover as much bare skin with a thin layer of water, and find a good breeze. In first aid situations, immersion in cool (not cold!) water works great. Less effective but still viable are alcohol rubs, where you swab exposed skin with rubbing alcohol (caution -- don't try this one around the campfire -- beware of flames).