To ensure a good cut, you must square the fabric first. After you have folded your fabric in half, take your long ruler, line it up top and bottom then cut. This ensures you have a straight edge to begin cutting. Always remember that no fabric, regardless of brand name/manufacturer is straight/square off the bolt. You have to square it for perfect cutting.
Hope this helps. GiGi
P.S. Remember, everyone was a beginner. We all made and continue to make mistakes. It's part of quilting. Good Luck. :D :D