Blackberry

I just finished a QAYG quilt and I had lots of trouble lining up the center sashing when adding the rows. I was just wondering if anyone knows of a super duper, never fail method for doing this. It isn't too, too bad but still I would like them to line up. Also on the blocks when sashing them together I can't seem to get the seams of the strips to match up. These were all made using 2 1/2" strips on an 11" block but even when I was putting them together I noticed that the very end strip was different sizes.