I used to design gear for my sorority (cool I know) so I have gone through tons of trial and error here
Girls, please note, this is a generalization I pulled from my sorority and student groups. Sorry if I say you like something but don't or vice-versa.
Things girls like:
longer anything, especially racerback ribbed beaters and plunging neckline v-necks
long sleeve shirts, especially waffle print
booty shorts/thongs
short athletic shorts (not super duper booty short, but girlie enough to be cute)
Accessories (sunglasses, new era caps, quare scarves, beer coozies, tote bags)
Bright colors, like neon and tie-dye (that could just be me. I'm a tad color blind so...)
Innuendos
Stealing shacker shorts from dudes... aka the basketball shorts you tossed her for her walk of shame. Come on girls, you know you have at least one pair. And if you don't... sorry for partying!
Things girls don't like:
Drowning in clothing
Anything incredibly tight, like leggings
Anything that says stuff on the butt. The last thing I need is a pair of UM Griz shorts that says "Paws Off" on the butt. Umm, pass?
Things only in light pink, baby blue, pastel purple, and bubble writing.
Shirts with capped sleeves
Short-sleeve shirts with an extra ring of fabric on the cuff of the sleeve. They never fit quite right.
Things that would only sell about 3 but would be kick ASS: an NS bikini.