My friend and I took a class many years ago. We were told to bring 3 15" quilt sandwiches. After teaching us about correct posture ( bent elbows should be even with bed of machine, which means either raising a chair or lowering the machine), we put on our gloves and began. On the first one we were to write our name in cursive with the machine a few times. Next we moved on to tracing a design on one and following the design with the machine stitching. We did many exercises like this using straight lines, curved lines, etc. We next tried the stippling. By then we were feeling pretty comfortable moving the fabric. After the class, we practiced at home a little more before beginning on a quilt. After that, without sounding like I'm bragging, both my friend and I can do beautiful free motion quilting.
As an aside, after I got a frame and a long arm, the free motion was so easy for us, and the ones who never learned it sitting down first have had a much harder time learning how to free motion.