For me the most important lesson was to measure twice and maybe twice again before cutting. When I first sat at my sewing machine, my sister advised me not to worry about the quarter inch seams or slightly off cutting as it would all disappear in the quilt. After having to remedy the inbuilt errors this slapdash approach creates I opted to be very careful with the basics. I find that when I've been ultra careful the progress of the quilt flows more naturally. I gave my sis a right telling off for having been a bad teacher !