I found out that the only way to learn to stipple is to stipple. But if you don't want to work with fabric and batting, try stippling using paper and pencil. Stippling is making a continuous line, so start at one corner and cover your paper. What you are doing is developing muscle memory in your hands which will transfer to fabric when you sit down at your machine.
When you get ready to try on fabric, start out with 9" or 10" square fabric sandwiches. This is a manageable size which is easy to move. If you use Insulbrite batting, you will have potholders / hot pads once you add a binding. Start out making large stipples and concentrate on making your stitches a consistent length. Remember, since you drop the feed dogs, there is nothing holding the fabric, so you can go forward, backward and side-to-side. The more you do, the better you will become.
Please don't compare your work to that of anyone else on the board. We are all learning every day. There is always a new techniques or new skill to try.