How do you set up your automations?

You can set up decision trees!

Sorry for the short answer -- I wrote a more lengthy reply but it got eaten before it posted.

Have you already taken a look at this help doc on automations?
https://help.bonterratech.com/everyaction/s/article/Setting-up-automated-workflows

the part to focus on is the decision step (which should be a saved search)

so a simple example might be a welcome series for new contacts

Original audience search is let’s say any new contacts created “yesterday”

Then a decision search: let’s say this search is “has donated”

if YES then send welcome email message A for folks who are new and have donated 
if NO then send welcome email message B for folks who have not donated

if you see the screenshot below this shows an example where YES ends the automation and NO sends and email -- but you could have YES send message A and NO send message B, if that makes sense