Clients want signed prints and I don't want my prints to be anonymous.
I always sign just under the printed image. If it is a silver print, I drymount it and sign on the mat just beneath the print, bottom right, in pencil. I then cut a window mat that is about 1" larger all the way around and show the signature. If it is an ink print I make the print a couple of inches wider than the image, sign with a permanent archival ink pen same as above and mat with a window mat same as above.
I use a super fine tipped black pen, which gives me a signature that doesn't leap out at you.