when hand stitiching, i use the same method sandpat described. not only because there are fewer layers to poke the needle through. when i'm done, i find i can press any way i choose. the stitching has not made that choice for me already. i almost always end up pressing to one side, and i press in the direction that will both highlight the piecing and make hand quilting easier.
when i'm machine piecing and plan to machine quilt, i press my seams open more and more often lately. it's easier for me to get nice sharp points and to line up intersections.
different methods work for different quilters. experiment until you find the methods that work best for YOU. :wink: