What Jane and Kathy said, also learning how to press without distorting blocks, esp. HST blocks. And, for those times when you need to be extra precise matching seams or getting good points when joining blocks or rows- use your sewing machine to baste all the intersections before sewing the entire row or block.
The way I do it is: 1. take a few stitches at each intersection (do Not baste in between the intersections). 2.open them up to see how they look 3. take out and readjust any that need it. 4. Sew down entire row or block making sure to sew exactly over the basting stitches when you come to each intersection. This has saved me a lot of ripping out over the years.
Rob