My experience and advice is going to disagree with some of the poster's above -- use the approach that works for you.
I don't use a lot of small sandwiches to practice. I do use them for trying out a new thread, evaluating a batting, or problem solving machine issues, but the actual learning is best done on a real quilt. I heard an instructor comment that learning to free motion on a little quilt sandwich is like learning to dance in a closet. you may be able to manage a few steps, but you really aren't getting the hand of it until you get out there and possess the floor. So when I was learning, I made a couple of quick, easy quilt tops out of charm squares or layer cakes. The fabric was pretty and busy and blended together well, which took the pressure off my quilting, as mistakes would blend in, and I could use a single color of thread. Then I just quilted those tops. Lots of breaks to relax and stretch. Lots of pushing through the parts I didn't like. But no ripping or un-sewing. Just keep going and see what works and what doesn't. I gave those quilts away, and while I don't love looking at them now (cringe a bit) the recipients love them and see nothing wrong with them.
I do not mark a design to follow. For me, that causes a lot of stress to try to stay on or near the line, and my stitching looks cramped and forced. Instead, I look at the overall quilt and think about a basic idea of how I would like to quilt reasonable sections of it. I may even sketch out a basic motif and variations on said motif. But then I just have at it and use the piecing as landmarks but otherwise free form it. My resulting quilting is much more fluid, smooth, organic and interesting.
I think the key pieces are support for the bulk of your project. For me, that means I lower my ironing board to be same level as my sewing machine table and place that to my left. I have a small folding table and some plastic bins I put on the other side of the machine (behind it) to take the weight of the quilt on that side.
I use needle down on my machine so that when I stop for a moment, I don't have the whole thing slide or pull.
I like using a grippy glove to help with keeping a secure hold on the quilt. I also do like using a mat to make the quilt glide more readily, specially when using a flannel backing.
I like using a finer bobbin thread for two reasons -- fewer bobbin changes and the quilting shows up beautifully as a textured pattern on the back, but without showing every wobbled stitch or backtrack. So my current favorite is Bottom line thread, but there are others. The spool may seem pricey, but look at how many yards are on the thing -- by the yard it's a great deal.
I always start a new quilt with a new needle. For some reason, FMQ wears my needles out (probably because you're not only putting a lot of stitches down, but there is also multi-directional pull or stress on the needle).
Have fun with it. I find FMQ to be the most enjoyable aspect of quilting. It wasn't for the first 2 or 3 quilts I did, but I now find it to be a great place to experience that enviable state of mind called "flow" -- where you are engaging brain and body completely but at an intuitive level very close to meditation. It's very much what my son describes feeling when he plays improvisational jazz, or some artists experience as they paint.