the one thing I learned that made all the diffence and most ppl might say, "duh", was that more important than the size of my seam allowances, was the size of the block itself.
I was always cutting out a block and then marking the 1/4" seam allowance with a mechanical pencil for the thinnest line I could get.
When I learned to measure for the "finished" block and then put the seam lines there, then I was getting accuracy.
I know, it may sound simple, or to some complicated, but it made all the difference between my feeling I was stumbling along, and I now actually becoming a quilter