That scant 1/4 does me in. I cut squares 1 inch larger than the finished block size. Draw a diagonal line, sew 1/4 inch each side of the diagonal. Cut along the line you drew, open up the half square triangles, press them. Now square up the units to 1/2 inch more than the finished block size, being sure to keep the seam line along the 45 degree line on your ruler and the seam going right into the corner.
There are many tutorials available on this method. Here is just one.
http://quilting.about.com/od/quickpi...uaretria_2.htm