Hi Dene,
Can you tell us what kind of sewing machine and foot that you're using? Can you provide a picture? Are you able to move your needle left and right? If you can that is a great help. It helps to consider sewing a scant 1/4 inch all the time. It really helps to have a 1/4 inch foot with the flange on it, worth every penny of it's cost.
You said you're not getting consistancy, have you asked yourself why? What are you doing different from piece to piece? Are you sewing too fast? Are you holding the fabric differently from one time to the next?
How are you preparing your fabric? Do you wash and iron it each time? Do you use sizing, starch or the new product Best Press? Do you sew and then press your seams before going onto the next? Do you set the sewn seam line before you open and press? Are you being consistent with every step from each time to the next?
However, I found with my 1/4 inch foot that I still needed to move my needle to help get the scant 1/4 sewing line so that my seams ended up being 1/4 inch.
I also have found a plastic open toe foot that has marking lines on it. I sewed sample seam lines until I knew exactly where to put my fabric edge and where the needle had to be to get the scant 1/4 inch. This foot was also worth every penny of it's cost. I like the open toe as you can see where the needle is going down into the fabric as you sew.
As someone else mentioned I have marked my sewing lines on some pieces depending on the pattern.
Pam M