I haven't made a signature quilt either, but I have picked up some tips by reading about others. The freezer paper on the back is universally recommended. Also you might want to put some tape around the edges of each block, or otherwise frame them, so people won't go right to the edge when they're writing. (You will be putting that part in the seam allowances but non-quilters won't realize that.) Provide more blocks than you think you will need, because some will get messed up, or someone may write something that you don't want to put in the quilt. Have someone watching the signing, to make sure the guests are writing with the pens you provide. Test out your pens in advance on the fabric you intend to use, and wash the samples to be sure the ink doesn't run or fade too much. Some colors of ink may work out better than others, so test all you intend to use.