IF there are no inset seams, I start left to right, bottom to top. That way, I can press the seams on each row in the opposite direction of the previous row which makes sewing the rows together much easier. I like to nest and pin the seams for a perfect (or near perfect) match.
One thing I do now (after having sewn the wrong side of two pieces together, is to open my seamed pieces and compare them to the picture. Avoids picking a lot.