On the front of the print, below the image, signature on the right and title on the left. I mat/mount leaving a margin so these are visible. It helps if you have attractive handwriting. On glossy paper I found a nice brush pen that looks good, on matte paper I use an "H" pencil.
Once matted/mounted, I then stick a label on the back of the mount with information about the print, usually a longer description. I found when showing at markets and the like that people will, most of the time, pick up the print and look at it then turn it over to look at the back, so I put something there for them to look at.
Anthony