I "sew" my patterns with a non threaded machine so I can see where all the lines are at.
I use a long basting stitch and I know where my fabric has to reach to when I flip it over.
I "pretend" to sew the first piece of a new section by using straight pins where the seam line would be...flip it and then if it's right, I don't sew it down until I've done all the other similar sections. That way I can keep seeing the proper way to place it before sewing.
My "add a quarter" ruler is a life saver...love love love it. Not part of them but love their product:
http://www.addaquarter.com/products.php