there is this little (test) to see if you are sewing perfect 1/4" seams...you cut 3 strips of fabric 1 1/2" x 6" , sew them together using your 1/4" seam then measure. it should measure exactly 3 1/2 " wide. if it doesn't you need to adjust...
one way to find your 1/4" is take a small (ruler) with 1/4" markings, place it against the needle, lower the feeddogs on the ruler, then put a small mark on the machine exactly where the 1/4" mark is on the ruler. you can purchase (seam-guides) which have a sticky side, or some people just use masking tape, running a piece at the 1/4" mark across the machine to use as a guide to follow as you stitch.
hope this helps, every machine is different and every one sews a little different, so finding YOUR 1/4" is a personal thing but necessary.
you can purchase a special 1/4" foot too.
hope this helps
ckcowl