Hypertherm discusses ways to improve cut quality in terms of cut angle, and dross, in a recent article.
Cut angle: Although the ideal is a square cut, there will be times when you wind up with a positive (more metal removed from the top of the cut) or negative (more metal removed from the bottom) cut angle. See tips to improve cut angle.
Dross: Although dross is inevitable when cutting with plasma, there are things you can do to minimize it as much as possible. Dross falls into one of three categories: excess dross, low-speed dross, and high-speed dross. See tips to minimize dross.