I usually divide the measurements by half; thus, if the floor plan shows the house as 44 by 28, I build it as 22 by 14. If a plan is for a far more expansive house, I divide by three. I do use grid paper and I typically re-draw the plans, but since most plans have a measurement for each room, dividing by half usually works for me. So if I translate the plans to be a 6 x 6 room, that's six clicks with the wall tool.
I only use plans and I usually replicate everything in them. I've come across some great house plan books at our local used bookstore and been thrilled every time.