I'm not sure what kind of set-up you have for determing a 1/4", but what I've found useful is a little tidbet that I picked up somewhere.
You know those stacks of post-it-notes, I'll take 1/2 of a stack and place it at the 1/4" mark and tape it down. I put the notes forward more and just a little past the needle in back. This way I don't have to watch my foot for an accurate 1/4". Its made sewing more enjoyable. :D