I tend to get really attached to certain victims, so clothing that reminds me of one or more of my favorite girls is a big plus. For example, Kitana is my favorite ryona babe. As a result, Kitana-style ninja masks are a HUGE plus; for me, any ryona can be improved tenfold by throwing a mouth-covering mask on the girl. Thigh or knee high boots and gloves are also high on my list of clothing to look for, and one piece leotards (especially ones with a bit o' cleavage) aren't bad either, although they take a back seat to the mask, boots, and gloves.
I was a big fan of Sailor Moon growing up, so girls in sailor suits and schoolgirl outfits are great. Mai Shiranui-style "kunoichi" dresses are a surefire way to drive me wild, like Kasumi or Maki from Final Fight, same with 90s-style athletic gear (thanks Sonya), and midrift baring outfits are cool, too, especially when the girl is wearing some sexy full-length pants and a tight shirt. I'm not that picky, though.
Overclothed is fine, and underclothed is good, too, but only so long as it "fits" with the character in question (the victim's costume is typically skimpy, they've got a "personality" that encourages revealing outfits, or they've suffered costume damage and the lack of clothing is the result of a gradual buildup) or the victim is a one-shot non-character or OC. Nudity is OK, but it has to be done in such a way that the overall "integrity" of the clothing is maintained. For example, going back to Kitana, I'm usually happiest when she's fully clothed. Having her top ripped open and her tits popping out is fine, but if she's going to be displayed full-frontal, she should at least keep her mask, gloves, and boots on.