Depending on how and when you want to grab the audit information. You for example can override OnInitialized method on CommonEntityBase and in there you can set such common audit fields:
this.SetNewFieldValue("thefield", value);
If the audit data in in another table (AuditInfo for example), you can take advantage of LLBLGen Auditors.
If you can set such fields before save, you can write an Validator an override OnValidateBeforeSave and set values there. Then you just need to assign such validator to your entities. You can use DependencyInjection for that, or set it in CommonEntityBase initialized methods.