I've released a number of limited editions for different artists and everyone has their preference, but as far as I can tell there is no standard. Some people do Number:Left, Title:Middle, Signature:Right, others just do it all on the right. Some artists like to sign in the white border, others don't like the white border and actually sign on the print itself.
What I've come to prefer lately though is having the artist sign once on the back of the print, frame it without a white border and then attaching a Certificate of Authenticity to the back of the frame with every little last piece of information about the print possible; who/where/how it was printed, date, number, signature, etc.. This seems to please collectors who want an unadulterated image to hang on their walls but still want the verifiable authenticity of a limited edition.