Maintaining a constant speed is good.
My machine has a slider bar to adjust how fast the machine goes. I usually put it on a middle setting then I can push the foot all the way to the floor all the time. This helps to keep the speed constant without having the machine go too fast.
If you are just starting FMQ put the machine speed on a slow setting so you feel like you are in control.
I recommend the Ricky Tims CD - Grand Finale.
Great demos on FMQ. I learned a lot.
I also took a class that was very helpful.
I have a friend who recommends to have the machine go fast
and move your hands slowly.