Try ironing the seam flat first before pressing to side. That seems to set the stitches and make seam flatter. I press to dark side of the fabric or alternate side I need to when joining seams. . Also when sewing put your top seam so that it pressed/lies to the left side and the bottom to the right . That allows the bottom seam to flow with the feed dogs and the top seam to be pushed/locked into the bottom. (make sense?). Also do not pin directly on the seam but rather on both sides of the seam after you have aligned up the seams by holding the pin straight. Pinniing directly on the seam will usually cause the seam to be off. Aslo I just heard at my LQS for their repair person to use you wider/regular sewing foot instead of you 1/4" foot when peicing. Just adjust you needle to make 1/4'seam. This allows the fabric to feed better/evenly thru the feeddogs .