Communications: "The Talk" - Too Much Skin
Either an employee(s) will be offended and report it, or you will see someone in the workplace in clearly inappropriate clothing.
Overly Revealing: I have dealt with females in very revealing garments (short skirt, low cut blouse...) and a male bodybuilder in a revealing harem kind of Halloween costume. The solution is to tell them that they are apparently unaware that their clothing is not appropriate for the workplace and request they either cover up with a jacket or sweater or change to other garments. Never had a problem beyond that.
Otherwise Inappropriate: A male employee showed up in a tee shirt bearing the slogan "Heterosexually Challenged." I felt it was borderline since he did not interact with customers but not the best choice in tops. So I waited and no one complained. Then I checked on him every day for a while and there was no repeat performance. Had there have been a repeat, I would have spoken with him about the situation.
Just employ judgment, maturity and common sense (and maybe helpdeskHR) and you will be fine.
Lance