I have attached a label to every quilt that I have given as a gift. The ones around the house that I have kept and the ones that I have donated have not gotten labels. I should label the ones I have kept....
I used to use a square of Muslin that I would write on with a Pigma pen and then sew on the back.
Not I use my embroidery machine and embroider on a piece of light colored fabric, incorporate is into a leftover block or some of the matching scraps and then sew on back.