I do different things for different projects. I don't prewash unless mixing new fabric with used (old clothes) or batiks. I never starch - just never tried it. I press my seams for most projects, but try hard to avoid pressing when working with bias cuts. If a project is a really simple one, I may not press at all until the end. It's hard to get seams to change direction once pressed, and sometimes I need to change them to eliminate bulk.