I make a label for every quilt I've made, even a raffle quilt. I think it needs to be on the quilt as part of it's history. It should include the name of the person/s who pieced it and quilted it (if different). Also the name of the designer of the pattern as well as the title of the quilt. I also include the month and year it was finished, town , state and if made for a specific person or event include that too. I've recently seen where people have included if it's won any ribbons at shows or at the State Fair.
I use Pigma pen or a Textile Marker pen. Instructions for heat setting the ink are usually on the packaging. I use a light colored cotton fabric or muslin. If you iron a piece of freezer paper to the wrong side, you can easily print on the right side . Also you can draw lines on the dull side of the freezer paper, which if this is held up to a sunny window, you can see thru, in order to write your info. on the label, while holding the fabric on the window.