Just make sure you have a quarter inch seam allowance. You can do a simple 9 patch by making all your pieces 4 1/2" squares then sewing with a quarter inch seam. If you're doing half square triangles, start larger. You can start with a 5 1/2" square, make a line from one corner to the opposite corner / then sew 1/4" from the line on BOTH sides. Cut between the sewing lines, press open then trim down to 4 1/4" squares. Most patterns online or in books that say 12" finished block are actually 12 1/2" until sewn into a quilt. Just keep practicing, remember that it's not rocket science or brain surgery, you can do it. Oh, and always relax and enjoy your new art. There are LOTS of sites with free quilt blocks and patterns--Quilter's Cache is a good one, luv2stitchpatterns.com, blockcentral.com, With Heart and Hands, etc. Just google "free quilt patterns" and see how many come up. There's thousands.