The British Ecological Society has produced a guide for those wishing to learn more about peer review. Although intended for ecology researchers, it is relevant to researchers across a much wider variety of disciplines.
"This booklet is intended as a guide for early career researchers, who have little or
no experience of reviewing journal articles but are interested in learning more about
what is involved. It provides a succinct overview of the many aspects of reviewing,
from hands-on practical advice about the actual review process to explaining less
tangible aspects, such as reviewer ethics."