I just finished my first FMQ quilt-- I hope my experiences might help you. Thank goodness I planned ahead and did a scrappy bargello out of busy 30's prints for my daughter. I named my meandering pattern "Spaghetti" since it meanders and crisscrosses a little. One side is definitely better than the first!
I figured just managing the bulk and getting the stitches done on this first quilt was an accomplishment. Even though I had done many practice pieces on 20" X 20" quilt sandwiches, moving that large quilt was different. Keeping a "nest" of flat quilt around the needle area by folding, bunching, and supporting the rest of the quilt was one skill I needed to master quickly. It's so easy to let the machine get away from you. Having a slick surface under the quilt is really necessary to have rounded curves and not jerky points. The quilt really does need to flow easily. Learning when to stop, with the needle down, to rearrange the quilt, remove any basting, and think about what I would do next improved with practice.
I have two vintage machines that are supposed to be good choices for FMQing, so I found the correct tension settings quickly on both of my machines. But, I realize it might take awhile for me to gain control over really consistant stitch length, especially in the curves. One of my machines makes bigger stitches when I'm stitching from right to left, so I'm learning to slow my hands down there while maintaining the same speed.
I got better as I found my rhythm and learned to relax. I concentrated on making rounded lines and consistant unquilted spaces. I used a finer poly thread for this project in a very neutral natural shade so my stitches wouldn't show as much as the heavier cotton quilting thread. But the thread color was also more difficult to see, so I had to find the right kind of lamp. I figure the puffiness caused by the unquilted spaces after I wash and dry the first time will further minimize my mistakes. (It also helps that my daughter loved the pieced top before I quilted it, so she doesn't seem to notice the wild FMQ).
I'm not sure if stitching in the ditch quilting would have been an easier choice for my first machine quilting project. I'm going to do some SITD to secure the outer edges of the blocks and one of the borders before I begin FMQ for my next quilt. It will have smaller areas of FMQ, not an all over meander, so I'm not sure how it will go.