In normal traffic coming to a stop; ie to a stop light I equally apply the front and rear.

When riding agressivively I'll use the rear break to slow down slightly before going into a corner but you never want to be on the rear break while actually cornering.

I've had multiple occasions when I unexpectidly come to a rapid decelleration or stop where the rear tire has locked and begun to slide out - a bit scary if you're not prepared for it but as others have said keep it locked up; otherwise if you let up the tire will instantly "rehook" and if the rear is swung out, it can cause a high side depending on how far the rear is out, as it immediately returns to a straight line.

-Clovis