I just got my machine, and I agree - just jump in! I loaded some muslin, and went wild on it with various motifs, feathers, swirls, whatever. I did a couple "samplers". My plan is to repeat the sampler in a few months, so that I can see my improvement (I hope). I've done 5 quilts now, and while I have a long way to go I feel that my quilting is quite passable. Here's a piece of one of my samplers. Not great, but you only get better with practice. Thinking about it doesn't make you better, unfortunately
There are lots of tutorials out there - for feathers and everything else. Drawing on paper first, to get the motion into your hand seems to be the main recommendation. Check out "365 days of free motion quilting" (google that) for lots of quilting designs.
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