You might want to check out Leah Day's website. She did a new design a day for one year. She now has an ongoing weekly email that goes out for free motion quilting. She gives all kinds of tips and hints.
The best advise I can give is don't give up. Keep trying. It will come after a while. Don't try to perfect all the different designs right away. First concentrate on one design and keep at that ONE until you feel comfortable with it. Then move on to another one. After you get a couple that you feel good with, then move one to some more. I try to have a practice sandwich next to my machine. When I first go to quilt something, I do some warming up, then move on to my piece.
Keep practicing and yes, doodle on paper too. It does help.