Draw it out on graph paper. I normally use 1/4" graph paper. If the block is small enough, I make it true to size. Otherwise, I let 1 square = 1/2" to go half size. Once you've got the block drawn out correctly, identify your pieces and group same fabric pieces together. Figure out the finished size of each piece, then add your seam allowance into the measurements. Test it in scrap material first before using the good stuff.