When a user fills out a registration form to an event, I can set the profile up to add him automatically to a specific group. But how do I choose the group automatically according to what he filled out in the form? Specifically, according to his chosen preferred language, I need to add him to 1 of 4 different groups. How can this be done?
This is what Smart Groups can do for you. So instead of setting the Group in the Profile, just set up a Smart Group based on the field eg language.
Or if you need people to be added to a Group via the profile AND then set up subgroups based on language, add the primary Group X via the Profile, then create a Smart Group based on 'is added to Group X AND has preferred language = Mongolian"