In May 2000 the International Committee of Medical Journal Editors (ICMJE; also called the Vancouver Group) revised its statement on authorship to read as follows:
Authorship credit should be based only on 1) substantial contributions to conception and design, or acquisition of data, or analysis and interpretation of data; 2) drafting the article or revising it critically for important intellectual content; and 3) final approval of the version to be published. Conditions 1, 2, and 3 must all be met. Acquisition of funding, the collection of data, or general supervision of the research group, by themselves, do not justify authorship.
The entire article from which the above statement is taken is worth reading.
http://www.cmaj.ca/cgi/content/full/163/6/716
Scholarship Access: Becoming a Student Doctor course
