Be sure you've ironed your backing fabric.
Be sure to hang your batting over a table or rod to flatten out the wrinkles from packaging or run through the dryer for 5 minutes on low heat to get the wrinkles out (LEAST favorable method)
Clip or tape each side across the middle FIRST as others suggested. Also begin your quilting from the middle to outside to keep the puckers out.
Relax and don't be so critical of your own work. The loft of each batting is different. If you choose a high loft or a poly batting you can get more puckers if you are trying to quilt to close. Read the batting package for the best width of quilting.
These are my best sandwiching tips that I've learned the hard way by not doing any of the above the first time. Since then I've developed a tendency to do it with every quilt to keep from ripping and screaming so much. :oops:
Hugs,
Sharon