I am just finishing my first OBW. I pressed the seams to the side and had a terrible time sewing the hexagons together (thank goodness this was a cheap-fabric-learning-experience top for my own use) . I went back to the tutorial here, and the person said to press the seams open (guess I missed that the first time I read it). In this case, it makes sense. Otherwise I also press to the side and light to dark.