When I make quilts and other items to sell or give away, I have commercially printed labels (find them on etsy.com). When I am entering a show (which I rarely do nowadays), I would use a small piece of muslin (3.5" square), write the required info on it, and applique it to the lower right-hand side on the back. Sometimes I do this if I'm giving the quilt for a special occasion (e.g., birthday, wedding, etc.).