I'm currently working on a OBW and the most important thing I've learned so far from the book is how to line up the six pieces of fabric with the print exactly the same on all six, and how to cut out the triangles.
Also, when you are putting the hexagons together, you only combine three and three, not the whole six. When you put the hexagons in a pattern on your design wall, then you can sew them together in a straight column by sewing the half hexagons together. I know, clear as mud. But that's what I learned from the book.