I've quilted about 5 queen size quilts on a sewing machine.
I can give some tips, but the most helpful one is that experience will improve each quilt you do. It might be easier to machine quilt a baby or lap quilt for your first experience.
My tips are to pin baste, which looks like you've already done. I pin baste by putting the three layers, quilt top, batting, and backing on a queen bed and sticking safety pins
all the way through to the mattress. After the quilt is literally stab pinned to the bed I take each safety pin and close it. This method meant less shifting of layers for me and the pins make it secure when I quilt on my sewing machine. Yes,
I can imagine this sounds so unorthodox to other quilters..but it works for me.
You can fold or roll the sides of the quilt so that it handles somewhat easier I prefer to fold both sids, leaving the middle of the quilt open to begin quilting.
Also, I quilt from the center of the quilt out, kind of like quilting pie slices from the center, start from a new section always from the center out.
I have quilted with stitch in the ditch, but prefer free motion quilting. If you want to free motion quilt, practice sketching on paper to get the feel, then on to some scraps of fabric with batting and backing. (You need some quilting gloves for quilting>it will also make it much easier.
Sorry for the long post, but hope it helps.