I have an adjustable speed machine and have it set usually at the medium speed. What I did was to watch the speed of the fabric as it went through while I was doing regular straight stitching and that gave me a reference as to how fast I needed to move the fabric myself while doing FMQ. As all the others have said, it takes lots of practice.

There are lots of great tips here but the same thing we hear time after time is practice. After a while it become second nature.

practice, practice and gloves sometimes when i am pushing myself to get a quilt done i am off on my stitches ,but when i am relaxed i can just buzz right thru it

Get out your practice pieces and turn on the MUSIC. Lots of times, it will help you get in a rhythm with your hands. Also,try standing and doing the free motion. It just takes lots and lots of practice. Good luck! :)