buy basic graph paper (quilters paper is great, but regular graph paper works fine and is cheaper). use 4 squares to an inch - this will make each square 1/4", so easy to add in seam allowances. With a PENCIL, start putting in the blocks you know about. Then it is easy to figure out how big your other blocks need to be. If you get an odd shape or still have problems figuring size, cut out your block and lay in on the paper and add your seam allowances. this will let you see the sizes without doing a lot of math. Little difficult to explain but as you try one that you already know, it will make sense.