Hi Sue -
Like you say, PRACTICE is the key. How to get the practice depends on your personality and what type of quilting you want to get better at. I know a lot of people practice on panels and you can get a lot out of them. If you use panels, look for panels with the types of areas you want to practice on. For example, if you do a lot of applique and want to get better at ditching around the applique, then look for panels with objects that you can stitch around. For practicing sashing areas, look for panels with simulated sashing. Things like that. The one thing that the panels won't simulate are the ridges that are created by the seams and applique.
My personality is such that I can't stand spending time practicing on an object that will be thrown away or doesn't have a particular purpose. So, I plan my "practicing" to be done on real quilts. For me, every quilt is a practice quilt because every quilt improves my quilting. When starting out, I chose my quilts and my quilting to match what I was comfortable with and what I wanted to work on. My first quilt was a basketweave where I did SID between the blocks using my walking foot and then put free-motion simple flowers in the center of each block because I know how to draw flowers and now I can quilt those flowers like nobody's business. The borders have vines with leaves because I can draw leaves and now I can quilt leaves. I used invisible thread on that quilt, but now I think that's a mistake when starting out because you just can't see where your quilting lines are so it's harder to do motifs. Instead, I would recommend matching thread that will keep your quilting subtle but still allow you to see the lines while you are quilting so it isn't so difficult.
Right now I want to improve my feathers. So, I try to incorporate feather motifs into my quilts. Every feather makes my feather quilting better, and I'm still finishing projects (as much as I can since I'm an ADHD quilter who flits between projects constantly).
I think the main thing to do is to not expect perfection. Instead, expect to do the best that you can and be pleased with it. As I always say, as long as the quilting holds the quilt layers together and the stitches aren't so big that you catch your fingers and toes, the quilting was successful and you have a beautiful quilt you can snuggle with and enjoy. Any beauty you can add beyond that is a plus.
Enjoy the process and please let us see what you are working on!