I love spray basting. It holds very securely throughout the quilting process and if there is a problem, I can always reposition the fabric.
First, I secure the backing to my dining table with masking tape (but I want to get some clips,) then I lay out the batting and smooth it down. I fold back one side of the batting and lightly spray. I carefully fold the batting back down on the sprayed backing, then do the same on the other side. I take extra time to smooth it all so there are no lumps or folds. I repeat the process with the quilt top. I flip the quilt over and smooth some more and repeat this several times until I have a nice, smooth sandwich of fabric.