I use to have that problem. Slow down and practice on fabric scraps first to ensure you have the right tension. Also, if you haven't checked it out - go to to a website
www.daystyledesigns.com and check out leah day's online tutorials. I went out and bought the Supreme Sider just a few days ago and have just completed an entire border without problems. I was amazed with the Supreme Slider. Wow - what a differenct it made in my free motion stitches. The website is an awesome resource for any quilter. I also purchased the teflon bobin washers and already have the gloves to control the fabric. The washers are amazing as well. I highly recommend. Solved all my problems. When you go to the website - click on the Free Motion Quilting Project - then START HERE button at the top and follow along - great tips.