Your colors and block layout are terrific.
Pin the seams like the others have talked about, then see if there is excess fabric at the beginning of your seam - if so, you can either match the end and work in the excess or sometimes, in my case, I have been able to trim off the excess before starting to stitch the seam....don't tell the quilt police about me - it works for me but maybe not others...I make very sure before trimming that the remaining fabric will not look skewed.
also, if you have everything matched and one fabric is looser than the other, put the looser fabric on the bottom when you stitch it..the feed dogs will help ease the extras into the seam evenly.
I agree with others about making sure you're using a scant quarter inch..and a quarter inch foot that truly gives you a scant quarter is one of the best tools a quilter can have.