Yes, it's complicated. But not all THAT complicated.
Consent is enthusiastic. "Well, sure, okay, if that's what you want," is not enthusiastic.
Consent cannot be given by someone who is intoxicated, underaged, unsafe, or subordinate.
Too many people overcomplicate it, trying to come up with a definition that could be used in court by one side or the other. But the point is not to avoid legal jeopardy, but to avoid doing harm.
What we need to teach young people (male and female) is to be a little more patient about developing enough of a relationship that consent can grow organically between them.
Consent should be a conversation. If you don't know each other well enough to talk about your feelings with regard to sex, it's safe to say it isn't time.