The answer is simple. At all times you need to maximize the available grip for either cornering, accelerating, or decelerating. Keeping in mind that your typical street tire can generate ~0.9 G of grip, while the brakes mated to super sticky tires can generate up to 4-5 G of deceleration force (in F1 cars), the ultimate goal to going fast, is to spend as little time braking as possible and as much time accelerating as possible through each turn.
The way our chapter's autocross is set up, those of us who offer our services to instruct gets about half a dozen laps before anyone else gets to drive. I usually take about 3 laps to get myself acclimated to the layout of the course, then I'll take one to two laps through WITHOUT USING MY BRAKES to give me a sense of the maximum speed attainable through each turn, and where and when I truly need to brake. Then the last lap I will fine-tune my brake point and accelerating point so that I'm either on the brake or on the throttle (no coasting through turns) while maximizing my time on the throttle.
One mistake that I see a lot of rookies, as well as more experienced auto-crossers make, is that you don't always have to brake late. You will be surprised at how much faster you can potentially be if you actually brake EARLY. It's counter intuitive, but I picked this up one time while doing a ride-n-drive event sponsored by a tire company. They have a few "pro" drivers there giving rides in between our sessions, and I picked the brains of one of the pros there, and he showed me that by braking late and nearly on top of the apex on a couple of the turns during my run, I'm actually giving up speed through the turns and the time-slips shows it.
The hell I don't! LISTEN, KID! I've been hearing that crap ever since I was at UCLA. I'm out there busting my buns every night! Tell your old man to drag Walton and Lanier up and down the court for 48 minutes!