I use nice stainless safety pins and start out on the floor. I slide my cutting mat under where I'm going to pin (carpeted floor, alas). Put maybe 20 pins total in (full size), just to hold the middle and keep the edges straight. Then roll it up and put it on a 6' x 3' folding table. Aha! Now I can put more pins/basting in without crawling around the floor!
Once it's up on the table, I'll put a few more safety pins/basting stitches in over the whole thing. Then I focus on the line or section I'm going to quilt -- pin or baste that area, then do the quilting, take the pins/basting out, then move on to the next area. Breaks up the job a little so not too much boring, nasty stuff all at once.
Usually I'll roll up the excess at one edge of the table so it's not hanging down and distorting things, but this doesn't seem to be a problem with a @ full size quilt and poly batting.
I've done only home-sewing-machine quilting so far. If I'm using the Pfaff with integrated dual feed, I use just a few safety pins, @ 3" either side of my quilting line and every 8-10" lengthwise; it feeds neatly, and things don't shift. If I'm using the old Singer 301A (does a better job with dense cottony batting), I'll baste instead.