Our Google Analytics Scheme

• utm_source = NL_[Customer code of Newsletter]_[Delivery date] - if a newsletter is set up in the campaign (NL for newsletter, format of delivery date: YYYYMMDD).
  otherwise: SAM_[Campaign code]_[Delivery date] - for other mailings, if no newsletter is set up in the campaign (SAM for standalone, format of delivery date: YYYYMMDD)

• utm_medium = [Format of Message] - e.g. email, app-push, web-push, voice, sms

• utm_campaign = [Name of Campaign]_[Message ID]

• utm_content = adId (ID of ad, if AdManager is used)
  otherwise: ln (link number - automatically assigned by link replacement)

More information: http://support.google.com/analytics/bin/answer.py?hl=en&answer=1033867