Go to Workspace>CRM>Interactions.  Select New Interaction.  Enter the Constituent and Interaction details.  For the Follow up:

the Date/Time must be tomorrow (or later)
at Type, enter Email
at Contact, enter the AssociationSphere User

Then during an overnight process, one email will be sent to the AssociationSphere User with the Subject Line "Your Upcoming Follow Up Items".

Note:  Make sure the AssociationSphere User has gone into User Settings and has selected "Turn On Email Reminders for Open Follow Up Interactions".