I've been selling fine art prints full time in 5 art galleries over the last 8 years. I also enrolled in several art and photo workshops. Here is what I do:
a) digital signature is out of question because art collectors give no value to such signatures,
b) I print on fine art papers and fine art canvas, and to remain consistent, I always hand-sign in the print (not in the margin). In other words, I do like most painters. This gives much more freedom to the buyer for the framing of the photograph.
c) I typically sign in the lower-right corner, but sometimes I do it in the lower-left corner if colors are better suited for that
d) I normally sign with a black pen (archival quality), but I sometimes use golden, silver or color pens.
e) I always sign with my full name so people can read who the artist is. I keep my signature readable and avoir initials, artist names, etc.
f) I avoid computer-made stylistic signatures, they all look the same and hide the personality of the artist.
As I said, it is what I do based on experience and discussion in art and photo workshops. In fact, there are no rules.
Yvan