Always use a sharp craft knife start cutting out the stencil. A blunt blade makes the task more difficult, and increases the risk that you'll get frustrated and less careful with it.
Begin cutting along the longest, straightest edges of the stencil design as these are the easiest. Your aim is to cut each line once only, so press firmly and smoothly.
Use your free hand to stop the acetate and stencil from moving off the cutting board, but keep your fingers well away from where you're cutting.
