We use a permanent fine-point marker on them. And yes, the handwriting is very small. We write RHPL (our library initials) the last 6 digits of the barcode and our phone number on there.
Megan Johnson
Teen Services Librarian
Rochester Hills Public Library
500 Olde Towne Road
Rochester, MI 48307
Phone: 248-650-5683
Fax: 248-650-7131