How do I put professional affiliations on a CV? I am currently a grad student in Psychology. I have heard that many professors like to see a list of 'Professional Affiliations' on a potential employee's CV, because it is an easy way to see whether the two people have common interests.

My question is, are there any guidelines for what I can realistically put there? Should I just list conferences in which I am a current, paying dues member; or can I put any conference in which I've paid dues in the past? Or can I be even less strict that these guidelines?
By 'Professional Affiliations' it is meant that one is a member of certain professional association such as IEEE, ACM, ICE, ASCE etc.

These professional bodies often arranges conferences which anyone can attend, so registering for the conferences does not mean that one is a member of a organizing body. Conference participation information may be put into your publication list as conference papers and/or given talks section.

So, You should only list the organisations as professional affiliations of which you are a member.