If possible, cut a bit large, sew and trim - especially for things like HST, FG and QST. I like my ruler that is marked in 1/8" increments - all along the ruler in both directions.
I also use thinner thread, and a shorter stitch length. When paper piecing, I grade the seams, since often you are sewing over them with the next seam.
I still have never used starch, don't find it helpful for how I sew.
And for learning, complete the 365 block challenge. It's got a bunch of 3" and 6" blocks and you start easy and get harder with smaller pieces.
Blocks like this become easy.
