I really struggled with 1/4 " seams for the longest time. I just couldn't keep them consistent.
I went to the pharmacy and bought some thick mole skin sheets (at least 1/4" thick this stuff must be...). I used graph paper to find the 1/4" mark from my furthest right needle placement, and I stuck a cut piece of mole skin on that line (I used the outside edge with a nice straight cut towards the needle side). When I butt my fabric to be pieced up against it, it has a nice little quide to keep me from wiggling my stitching line.
This is really the only reason I kept trying to piece quilts. Otherwise, I think I would have given up.