everyone has different ways of doing things, so I will tell you mine. I do my own quilting as long arm service is more than I choose to spend.
I started out laying the backing fabric on the floor and I would tape the corners and a few places on the sides down to keep it straight.
then I layed the batting down and smoothed out the rinkles, then the top.
I started pinning with safety pins starting in the middle and working my way to the sides. I made sure I pinned at least every 4 inches or so, keeping in mind how I wanted to quilt it.
when done, I shoved half the quilt into my machine and using gardening gloves with the rubber dots on them (to keep a good grip on the fabric) and I start my free motion quilting. In the beginnning I did just an all over meander. Now I can do other designs, but that takes practice.
Since my knee is out of wack I am using a 6ft banquette table to lay my sandwich down on and that seems to work very well, the weight of the fabric seems to keep the layers straight.
Some people tie there quilts and some hand quilt them, but this is my method
hope it helps, feel free to pm me if more help.
When FMQ I use a darning foot and put my feed dogs down
You could also stitch in the ditch instead of FMQ