When you're creating your resume, think of your work experience and education as your foundation and the "extras" like professional organizations as the lip gloss. Adding your professional affiliations to your resume is not something you put front-and-center, but they do show that you're committed to improving yourself and making the connections that can give an entire company a little extra sparkle.
Location
Your professional affiliations or memberships are an important part of your resume, but they're generally not something you want to highlight near the top. As a general rule, a resume starts with a header that contains your contact information, followed by a "Skills" or "Work Experience" section, followed by an "Education" section, and possibly a "Technical Skills" section. After that, it's common to include a "Memberships" or "Professional Organizations" section -- though some people do opt to flip the last two sections.
Contents
What you choose to include in your "Professional Organizations" section may be specific to the type of work you do, and also the amount of space you have left on your resume. If your resume is getting close to being more than two or three pages, keep this section brief and only include the name of the organization. If you've been extremely involved in a specific organization and have held titles or have been a primary organizer, include a few sentences or bullet points about your involvement. And if you know that one of the hiring managers at the new company is involved in the same organization as you -- mention it more than once by saying something about it in your cover letter.
Past Affiliations
In some cases, you may have been part of an organization at one point and have since let your membership lapse. When that's the case, and you still feel that the membership is a valuable addition to your resume, include the months and years during which you were a member. You may also opt to include a line stating why you are no longer a member, if you feel it is relevant to the job at hand.
Conflicts
When you're applying for a job at a new company, take some time to consider whether including the membership is beneficial for your job prospects. In some cases, being a member of certain organizations may make you look bad. For example, being part of an anti-abortion group may not benefit you when you're applying for a job at Planned Parenthood; being part of one union may not benefit you when you're applying for a job for which you'll need to be a member of another union. Weigh your options carefully and tailor your resume to each and every company to which you're applying.
