It helps a lot to have a large flat surface even with the bed of your machine. Here is a link on how to make a custom table top without spending much money:
http://www.youtube.com/watch?v=g14go...os=55QRg2W_NIs
Start at the middle of the top and work to the bottom, if possible. Then do the same starting at the middle of an edge and working to the opposite edge. The middle is the hardest part to quilt because there is the most fabric under the arm. I have found that loosely accordion-pleating the sandwich under the arm is better than rolling (provides more flexibility).
You can also split the quilt into 3 parts (without the division showing later) to make the bulk easier to handle. To do this, you layer the sandwich as usual, pin back a third of the top and backing fabric so it is out of the way, then cut the batting only in large S-shaped curves. Mark both sides of the cut so it is easy to reposition the two pieces later. (The curving cutting line helps with the repositioning later and also hides the join.) Pin the top to the backing fabric. Do the other side of the quilt the same. Machine quilt the middle section, leaving a good 4 inches or so free near the cut edges. When the middle is done, re-attach one side of the batting with hand tailor tacks (or some people do it with a long and wide machine zigzag) and re-position the top and backing over that section. Complete the machine quilting on that side. Repeat with the other side. Marti Michel has a book on how to do this, but I first saw this process described in detail in another book by another quilter (whose name escapes me at the moment).