Dear Dr. Date,
I am the friendly janitor in Wulling Hall. Day in and day out I am bombarded with the wonderful sight of wandering female students. Under normal circumstances I would not have problems engaging these “would-be prospects.” Unfortunately, the five-hour training course on sexual harassment the U of M gives to all new hires has left me feeling quite wary of approaching the students. So to all lovely female wanderers: Feel free to engage me in meaningless chit chat. What could be a greater turn-on than seeing the man of your dreams clean out a public rest-room. Rhetorical question. Thank you for your time.
— The friendly janitor

Yes, sexual harassment is a big issue that organizations like the University take very seriously. Generally, however, I’ve found that it’s the people that squawk and whine the loudest that need the five-hour session the most. If you listen carefully to what the seminar leaders are saying, you’ll realize it’s all about power, or more appropriately a misuse of power.
As a staff member of the University you are not automatically restricted from talking or even dating students or other staff. The problem starts when you begin to pressure a prospect or make inappropriate advances that in any way make a person uncomfortable. This doesn’t pertain to your letter, but you should also stay away from co-workers you supervise or who supervise you.
The best bet might be to only flirt with women while at lunch, but since you seem determined to mix business and pleasure, here are some plausible lines you might use and my nonofficial opinion of whether they’re OK or not.
“Hi!”: This is fine and friendly, but if you’re looking at, or worse, ogling certain parts of her body, you’re still in trouble. Remember that humans communicate with each other on many different levels.
“Hi! Wanna go get a spinach and goat cheese pizza?”: Technically legal, unless the prospect has refused date offers from you in the past and you just aren’t getting the hint. Remember also that at a bar it may be everyone else’s problem if you sound and look threatening, but at work it’s yours.
“Hi! You’ve got a righteous ass.”: Only appropriate if they’re actually accompanied by an honest and upright donkey, at which point they’d be violating various other University rules regarding animals in buildings. As a janitor you should probably escort them outside before you have to clean something smelly off those floors you just mopped.