When creating a new pack you'll find a section near the bottom of the form, where you'll be prompted to choose:
how many credits the customer receives
what kind of credits they are (dollar or class/appointment credits)
and what these credits can be used for
This last section will default to including all existing classes, so make sure to uncheck any that should not be included. It will also default to not including any appointment services, so make sure to include any that need to be added to the list.