I'm convinced that good piecers are good pinners. Nine years, and 235 quilts, after I started piecing I still use a lot of pins. One thing to make sure of is that you are sewing a true quarter inch seam. Use an index card and sew along a printed line, without thread, until you know exactly where your quarter inch is on your machine. I've taught three people to piece and this is the step I always start with so they will know where a quarter inch is and so they can practice sewing a straight line.