down
mod. prepared; knowledgeable.Are you down for the test tomorrow?Everything's down for the party.
fly
mod. knowledgeable; alert and in the know.This dude is fly; there's no question about it.We don't need any more fly birds around here.
in the know
mod. knowledgeable (about something); having inside knowledge (about something).Ask Harry. He's usually in the know.Sure, I'm in the know. But I'm not telling.
know which end is up
tr. to be alert and knowledgeable.Don't try to hustle me, sister. I know which end is up.Poor Jed doesn't even know which end is up.
on the ball
mod. knowledgeable; competent; attentive.This guy is really on the ball.If you were on the ball, this wouldn't have happened.
savvy
1.
n. knowledge; know-how.
She really has savvy when it comes to clocks.I don't have the savvy necessary to do the job.
2.
mod. knowledgeable.
What a savvy gal!She is truly savvy!He is one of the most savvy directors in New York.
wise to someone or something
mod. having found out about someone or something. (Underworld.)The cops are wise to the plan.I'm wise to Lefty. He's a wire.