Omnigrid are my favorite. To start and stay with the same brand is one key. Accurate cutting is another key. But I have found in the past year and a half STARCH is the best thing I do. Starch every piece BEFORE I cut anything makes for better cutting, better piecing, less pinning (no pinning) , better quilts. I starch and press dry every piece stiff before I do anything else. Using the same machine start to finish makes a big difference. Pressing carefully makes a difference, an accurate 1/4 inch seam is also very important. Maybe some of this will help you.