What kind of machine do you have? Most of us use a darning foot for FMQ. There are two types, I think. Mine is a "jumping" foot -- has a spring in it so when needle goes up, foot also lifts a little to allow easy sliding of the quilt. The other type is a "floating" foot -- no spring, and just floats a little higher than a regular foot, again to allow easy sliding of the quilt.
If you Google "sewing machine foot for free motion quilting" and then click on "images", you will see what this type of foot looks like for different machines.