I heartily second all the tips that Stephanie (K9 Dancer) on page 3 listed as she uses when teaching. To that I would add that which helped me cross over into the world of FMQ:
Prepare a practice sandwich at least 12" square. In regular, medium-length stitching mode (after checking your tensions to ensure you're getting a good stitch), with a regular (or walking) foot, feed dogs UP, etc., stitch a grid work about 1-1/2" apart.
NOW, change your top thread color, drop the feed dogs and put on your FMQ/darning foot. Start stitching from left to right about a quarter-inch from the first line of stitching, attempting to duplicate the stitches that were regulated by the machine. (The first ones are usually pretty much garbage. If not, you're ahead of the game already.)
Then, repeat the next line of FMQ stitching a quarter inch from the one just sewn, again trying to keep your stitches appearing as close to the regulated line as you can. (The second one's a tad better.)
Now, keep doing that all the way across. You should begin to see some improvement.
Turn the practice piece around and do the same on the next grid all the way across.
By the time you get done, I'll betcha that you'll be pretty close and will have developed a touch, a coordination that really works for you.
You got nothing to lose but a practice sandwich.
Hope it works for you.