Hi Judith...I'll try to give you what "little" I know....I have tried all sorts of ways to seam these...
1/8" seams, one little misstep and you are off the seam allowance and in the deep dark realm of knotted fabric in the bobbin area...maybe others sew better than I...so all my seams are 1/4".
Most of my quilts are made from someone else's scraps, i.e., waste triangle corners so when I sew them they are a little oversized; I cut them to the largest size I can make them to the nearest quarter inch. Because I recut them, accuracy in the HST stage is not imperative. I got so tired of making HST's, I paper pieced flying geese strips (there are 2 FG quilts on the tree)....sometimes I press seams open, sometimes to the side..I've trimmed seams, but usually don't. After ever step, I square the blocks up...like in a lot cabin...every log gets squared after sewing......oh and starch is your friend...good luck..