nine patch blocks can be made any size you want. usually the size of the block is divisible by 3 to make cutting the patches easier. if you want to make a 12" block, each patch would be finished at 4", so you have to cut the patch 4 1/2" to add the seam allowance. here is a link to the directions for making one
http://www.quilterscache.com/N/NinePatchBlock.html .
here is another great site that gives LOTS of info about hand-piecing. there are directions for a 9-patch by scrolling way to the bottom
http://serenapotter.wordpress.com/ca.../hand-piecing/
welcome to the board and be sure to post pictures of your progress. don't be afraid to ask questions!