From my observations, tracking codes are generated by the individual creating the campaign. Your organization can set guidelines to establish governance over the format of this tracking code.
From there, you can place the tracking code inside a query string of your choice. For example, http://example.com/?cid=my_tracking_code. You can use whatever query string you'd like, just make sure it's consistent.
Once the query string is in the URL, you can pass the query string into the Tracking Code variable (s.campaign). There are several utilities that allow you to easily integrate it.
Data Elements in DTM can capture query strings
Util.getQueryParam can capture query strings outside of DTM
Once data is collecting, you can view the tracking code dimension to see the performance of campaigns.
