After getting Harriett Hargraves and Diane Gaudinski's machine quilting books I learned this great tip... Both recommend, after pin basting, SID to help stablize the quilt for FMQ. I tried it and it made a world of difference. You can take out the pins once you have SID a grid which makes the quilt much lighter and easier to move for FMQ. Say you have 12" finished pieced blocks. You only need to SID around the blocks not on each element within the block.
Oh and when SID, they both recommend doing all your horizontal lines before doing any vertical (or vice-versa, do all vertical then all horizontal)
Start in the middle and work your way out. As you work to the ends it gets easier becasue you don't have all that bulk in the throat of the machine.
They also stress a good work area where you can sit comfortably and pay attention to how you hold your arms so you don't fall into the bad habit of raising those elbows up like bird wings which lead to stiff neck and fatigue.