I've found (for myself at least) is the walking foot works the best for keeping the intersections aligned and for keeping my 1/4" perfect. I align the left side of my walking foot (Babylock) along the sashing stitching line, then adjust my needle to 1/4" from the right side.
Jenniky - the extra pinning of the blocks is a great idea. I'll have to try that when I start working on my next project. Hope to have something to post soon.