For example, I tend to use the following format: universe-series-book-location.
Universe only where necessary.
So, as an example, we'll use my Vegas Paranormal Police Department …
Universe: Paranormal Police Department (PPD)
Series: Vegas
Book: The Merging
Location: Facebook Ad
My common id would be: ppd-vegas-merging-fb-ad
… some folks don’t get that granular, though. They want to target everything that fits the PPD Vegas section, so they’d use:
ppd-vegas-fb-ad
…or…
ppd-fb-ad
Whatever works for you is fine. Just try to use a convention that is consistent so it's easy for you to maintain across your books.
Now, those events will show up in the events manager on Facebook:
...and then...
So that will set up the audience for the ppd-fb-ad Common Identifier. From there, you can click the "Include more people" option (shown on the screenshot) and add another Common Identifier if you want. You can do as many as possible.
Cheat sheet for some of the ones I do:
ppd-fb-ad (fb-ad = Link clicked from my Facebook ad)
ppd-fb-page (fb-page = Link clicked from my Facebook page)
ppd-fb-group (fb-group = Link clicked from my Facebook group)
ppd-bb-review (bb-review = Back of Book Review link)
ppd-bb-nextbook (bb-nextbook = Back of Book next book link)
ppd-nl (nl = newsletter...so any link I put in there, you could add -review, -book, etc.)
ppd-bub-ad (bub-ad = BookBub ad link)