I don't think the rules of dating have ever changed really..
With what to wear I suggest something nice but casual, a nice tip with a good pair of jeans and cute flats is always good plus its for coffee so you don't want to look way over dressed.
With makeup it totally depends on how much you usually wear, I don't wear much makeup so if I am going out I will wear a bit more foundation coverage than usual, some mascara and some lipstick instead of a lipgloss. You don't want to look different just fresh
Wear your hair in a way that makes you feel confident, I know if I wear my hair down and straightened I have a little more sass than usual
plus guys seem to like it when women wear their hair down for some reason :S
Good Luck and have a great time