I got a whole heap of responses!
Everything y'all said fascinated me.
Obviously, I think some of you responded with tongue firmly in cheek, but the variety of the responses were nonetheless revealing. As far as I can tell, there really isn't a right way or a wrong way to compliment someone. You could go with articles of clothing, or you could refrain from mentioning clothing at all. You could be extremely passive and avoid the situation altogether, or you could make sure they won't forget you by doing something outlandish.
I think, when it comes to compliments, you need to work with what works best for you. If a compliment doesn't go over well, then maybe that person doesn't like your style, and that may indicate you guys aren't a great fit. Or it may indicate your crush isn't a 'Words of Affirmation' kind of person. If you don't know what that means, I would recommend checking this out.
As for me, I only really have two rules. First, I never say 'today' in any of my comments. "You look nice" could refer to always. "You look nice today" might suggest that they look like garbage every other day. In addition, I try to focus on things the other person can control. If I say, "Your face is well-constructed and symmetrical," well, that compliments them less than their genes. But if I say, "I really love your thoughts on the political situation in the Middle East," well, that shows them you care for more than their body and you're a great listener!
So now that you're all ready to compliment your crush, let's see how you do!
You walk up to your crush, swaggering with confidence.
"Oh hi! Your shoes are gross. I mean nice tasty. Uh, today is what I said. Trying to say. I mean, let's fight? You're stupid."
Welp, there you go, running off into the sunset. Better luck next time, I guess.