You open the report and the same campaign appears three times: newsletter, Newsletter, news_letter. Each row is small enough to overlook, and until somebody adds them together the campaign looks smaller than it was. That is usually the moment a channel gets written off.
UTM parameters are labels appended to a link. The tool takes them literally and has no idea that two spellings mean the same thing. Changing tools does not fix this; only agreeing a convention and writing it down does.
What each of the five fields answers
The pair most often confused is source and medium. Source is the specific place; medium is the category that place belongs to. Inventing a fresh medium each time destroys the grouping in every report, so it is worth fixing the permitted medium values as a short list.
Four lines of convention are enough
Short conventions survive. Lower case only; hyphens instead of spaces; medium chosen from the agreed list; campaign named period-then-subject covers most real work.
Then write it down. When several people build links the convention will drift, and the drift only surfaces in a report weeks later. Keeping the values already in use in the same document helps even more — people copy an existing spelling instead of inventing one.
Never put UTM tags on internal links
This mistake is common and expensive. Tag an in-site banner or menu link and, the moment a visitor clicks it, the tool may treat it as a brand new visit. One person who arrived from search and clicked a banner is recorded as two, and the original source is overwritten by the banner.
If you want to know how an internal banner performs, record it as an event instead — the naming rules from the previous part apply unchanged. UTM tags are for links arriving from outside the site, and nothing else.
Check the link before you send it
Click the finished link once yourself. Confirm the page opens correctly with the parameters attached, and that no redirect strips them along the way. Some link shorteners drop parameters too, so a single check before sending is worth the ten seconds it costs.
Making operational conventions stick across a team is covered further in the development workflow archive, and if you would like the site’s speed, indexing and security reviewed as one job, that is what our optimization program does.
Next part
The more accurate the data becomes, the heavier the question of what you are collecting gets. The next part covers privacy: collecting the minimum, disclosing it honestly, and deciding a retention period on purpose.