girls in hats can look great.
things that look good:
relaxed look
pony tail
jeans
curved brim
beat up hat
things that look retarded and if you do this, don't bother wearing the hat:
flat brim
hat backwards
hair all over the place - not a mess, but the even distibuted, "I spent a lot of time on this, yet still put a hat on" look
and THE worst thing you can do with a hat:
put your ears up underneath it - I've not *once* ever seen that where I thought it looked remotely cute, cool, or even normal.