Finish braking before you turn in. Measurements show this is what separates novices from skilled riders: short, sharp braking instead of dragging through the corner.
In an off-road corner instrumented with a brake power meter the difference showed up in the data: inexperienced riders did more braking work over a longer braking time but at lower braking power — and were significantly slower for it. They also leaned far more on the rear brake. The underlying fault is always the same: turning in while still braking. A braking tyre has almost no cornering grip left and washes out. Instead, pick a fixed braking point on the straight, brake hard and briefly there, come off the lever at turn-in and accelerate out. Roughly 70% of your braking force comes from the front wheel because weight shifts forward under deceleration; the rear only stabilises. The caveat: 70/30 is a rule of thumb. On steep, loose or wet ground, feed the front brake in earlier and more gently — grabbing it with straight arms is what sends you over the bars.