Priorities define the importance given to the sound or motion object in relation to other objects within the same Actor-Mixer structure. Establishing general priorities for parent containers early on at the top level of the Actor-Mixer based on sound type is a step in the right direction. Additionally, identifying critical sounds in need of a higher priority to ensure their playback is a matter of knowing the content and, where possible, organizing it appropriately to make things easier towards the end of a project.
You can also alter the playback priority based on the distance the sound or motion object is from the listener. Wwise applies an offset to the priority using the Max distance values defined in the Attenuation Editor. The amount of offset applied will depend on the object's relative position to the listener. Wwise linearly interpolates the offset between the source point, where no offset is applied, and the attenuation max distance, where the full offset value specified is applied.
Managing priorities can be done in the advanced setting of any sound object, Actor-Mixer, or audio bus in the Advanced Settings tab of the Property Editor.