I machine quilt on a frame and start at one end going left to right.

I start in the center. I don't have good luck any other way.

I start in the center and work my way to the outside.

Klgreen,
Are you using a walking foot? If not you need one, it makes quilting so much easier. I do a line of quilting in
both directions, it helps to stablize the quilt and then I quilt from the center out.

I do the same thing as purplefiend. Using my walking foot and a slightly bigger stitch, I quilt one line down the middle lengthwise and then widthwise. Before quilting these lines, I also use straight pins 3 or 4 inches apart all the way down the seamline to keep it taut and pucker free. I remove these pins as I stitch. This stabalizes the quilt and I can then go ahead and quilt each section. I also find that the batting makes a big difference. Cotton batting makes a smoother, flatter product with a smaller chance of puckering. I find polyester batts much more likely to pucker on the back, even if the quilt is pinned really well. If your backing is polyester/cotton it is also more likely to pucker or shift.

I have a walking foot. I ususally use that for the binding, but I'll try that today when I'm quilting again. I do use the biggest stitch on my machine which is 4, but the stitches arent the same size 4 as when you are just sewing two pieces of material together. Maybe with the walking foot they will be....can't hurt to try.

I do alot of stitch in the ditch and have not started in the center for ... about 10 years. I have done stitch in the ditch starting from one side corner and working my way down and across the quilt. I would not have done this in the "old days" prior to spray basting and a walking foot.
Believe it or not I have not had any issues with puckers or tucks ... it looks the same as if I had done it the traditional way of starting in the center and working toward to outer edge.

I start on the borders first. That way I can trim off all the extra backing and batting so I woun't have so much to push through the machine. I spay bast my layers together and pin if I have to....haven't had any issue with this for stitch in the ditch or free motion.