It depends on what kind of batting you're using. If you're using high loft, poly batting, it may be impossible to get no puckers when machine quilting just because of the puffiness. Use a flatter cotton batting like Warm & Natural. Definitely make sure you iron the top and backing FLAT. If it won't lay flat use starch - it can be a lifesaver if you let it sit a bit before ironing, it will take up slack areas by 20% or more. Then iron them flat taking care not to pull things out of place.
Then tape your backing down - making sure it is tight. Apply the batting, which you have let hang for a bit out of the package to de-wrinkle, and tape it down too making sure it is taught. Now place your IRONED top overtop and start pinning in the center. Don't pin too close together because it can distort the layers. When you're sewing, make sure you take out the pins before you get too close to them. And check often that the backing is taught and pull it taught if you need to. And if it's a tiny tuck - just keep sewing because only you will notice it's there.