I draw a 1/4" line on each piece before I sew it. For years I tried to do it w/out that level of detail by marking a line on my machine with a nice edge, but the seams were still not consistent. That worked okay with some quilts, but when I did my first feathered star block it was imperative to be accurate. And it went together beautifully so now I use this method all the time. Though it is very time consuming, I've found it's not near as much as ripping out pieces to correct the wonky seams.
And I'm much happier how everything goes together so easily when it's time to assemble the blocks. I've decided this is a hand/eye coordination problem. I can see what I want to do - I just can't execute it easily without help.