Rush88888 covered most of it. You need to be sure your ruler remains still, but it is also possible to waver from the edge of the ruler if you are nit careful. Try to hold the cutter at a consistent angle. I use a June Taylor Shape Cut (1/2") for almost all of my cutting because I have to sit while I cut and it make it easier for me to keep my cuts true. as you go along, please remember to sharpen or change blades regularly. Dull blades chew the fabric, rather than cutting it and are much harder to use. As much as I hate ironing, having your fabric freshly pressed does matter in getting good cuts.