Maybe the reason there are so many variants is because there is no one best way.
I would never sign on the print, and I CERTAINLY would not use a rubber stamp.
For prints that are mounted traditionally, with an overmat and in a frame, I use pencil to sign the mat at the lower right corner of the window, and put the date at the lower left. Sometimes I write the title, centered.
For canvas wraps, I print a label, about 4x6 inches, with the title, date, description of the print (e.g., Medium: Archival digital inkjet (giclée) print on canvas), a brief blurb about print care, and a place for my signature. I attach this to the back of the canvas.