I had the same problem of blocks not being the right size when I first started sewing 1/4" seams.
After many classes with great instructors and knowing my fabric is cut to size I learned:
1. Use thin thread in top and bobbin
2. Press my seams open or tug and press the seam to one side. Keep iron in place longer for it to do it's job.
3. Twirl intersecting seams open
4. Use a longer stitch length 2.5 and backstitch at beginning and ending.
5. Keep index finger against the left side of the foot when coming to the end of the seam. This keeps the seam from veering right.
6. Sew slow, slow enough to count each stitch until you can tell by sight the seam is perfect.
7. Hard to match seams, glue baste them then sew.
One thing I learned that has held true and it's not known by most is if you are cutting strips of fabric you have to true up the edge after the amount of cuts the width of the strip. Example: if you are cutting five strips at 2 1/2 " you have to true up the edge after cutting 3 (rounded up) strips. Pieces cut 5 inches you have to true up the fabric edge after 5 cuts and so on. This is where a lot of frustration comes from, fabric being cut just a tad off even thought it looks fine.
One thing I forgot. I guess because it has become second nature to me now. I use a clapper to flatten all my seams after pressing.
Last edited by BellaBoo; 10-17-2013 at 06:34 AM.