Hi Diana, in general, any form of quilting that is not a straight line is considered free motion. You can follow a particular pattern or you can do your own thing. For example, I like stipples, which is squiggly lines that never cross each other, or loops, which is just that, loops. Sometimes I just outline the borders of the design printed on the fabric. For the machine, I use my old Bernina that is 30 years old. You can use almost any domestic machine, but you need to practice a lot and test the setitng on your machine. There is no magic number I can tell you that will make it work for you, but you need to adjust the tension on your machine, almost for every quilt. Any little thing can affect the results. I find that different thickness of batting affect the final look of your quilting. Also, how heavy your quilt is. If you have a small table and try to quilt a big heavy quilt, the weight of the quilt will pull and change the tension. As you can see there are many variables that to consider.
As mentioned before, the best thing to do is to practice. It will get better with time. I sell many quilts and have my own online store for my quilts, and 6 years ago I walked out of a machine quilting class because I couldn't do it.
Good luck,
Maria