I've done several things - I have hand embroidered two, but it takes too long for my taste. I've done many with a pigma pen, which works well but if I don't format the wording on a printer and then trace, my handwriting is a little sloppy looking. I also have a book of iron-on transfer labels, and they are cute, but sometimes not exactly what I'm looking for. Most recently, I got a bunch of little alphabet stamps and a Versacraft ink pad (special ink for fabric; heat set and it is permanent), and I've been stamping my labels. It is more time consuming than writing, but fun, and looks more professional. I can stamp little flowers or butterflies or whatever on there, too, and color them with fabric markers. This is my new favorite way. It costs more than embroidery or pigma pens (the ink pads and the stamps, fabric pens, etc.) but less than buying an inkjet printer.
I usually put who the quilt is for, the occasion, if there is one, my name, and the date (month/year)