Elbow Above The Shoulder
If you been around quarterback camps or clinics, you have probably heard talk about having a high elbow during your throwing motion, and if you haven't, you are going to now. Having a high elbow your throwing motion means that before you start your extension phase of your release, that your elbow joint is above or higher than your shoulder joint. This allows a quarterback to extend his/her arm directly to their target for improved accuracy as opposed to more of a rotational motion where the arm slashes across their body.
Continuing to use Drew Brees as an example, you can see how all of his force generated during the throwing motion is being directed at his target by fully extending his arm straight towards his target. A product of the outward direction of his force is that his arm is not going across his body post-release of the ball. Instead it is falling in a downward angle because he is not over rotating on his throw.
Here is a drill from a Sean Shelton Quarterback Academy Camp to help Quarterback get comfortable throwing with a high elbow: