I use moleskin to keep my 1/4" seam accurate. It works much better for me than any foot or gauge I have tried. Moleskin is found in the foot department of pharmacies; I like the thick stuff best. Basically I place my presser foot on a ruler and lower the needle until it is at a scant 1/4". I cut the moleskin into strips, remove the paper from the adhesive side of a strip, and place it on the bed of the machine aligned against the ruler edge.
One of the advantages of using a hard right edge like this is that it requires much less concentration to feed the fabric through the machine, and I can go much faster with this than I can with a 1/4" foot or by following markings.