Approach a woman who does want to be approached at the time she wants to be approached without communicating any of that information. Ez. /s

In seriousness, consider class time as ‘work.’ Don’t bother women at work. Now if you’re in the back of the class and she’s browsing Amazon, maybe she’s not working as much but don’t be creepy and say “I see you’re shopping, talk to me instead,” because, ew, but at least you know next time you’re getting situated you can say “Hey, stupid question, blah blah blah” and test the waters.

Or, just generally treat women like people. That one always works.