Draw every UTM value from an agreed, restricted list — never free text. Source is the specific origin, medium is the mechanism, campaign is the program. Publish a UTM builder so nobody hand-writes a URL, and translate the values into your CRM's source and channel fields with one documented map.
The convention matters less than the enforcement. The failure mode is thirty spellings of "linkedin" and a channel report nobody trusts. Start from a standard taxonomy and tailor it rather than starting from a blank page — most marketing teams have attribution experience but haven't gone deep, and editing beats inventing.
Every claim above comes from work LeanScale published. These are the sources.