How to log actions?

Hi,

I want to log data-modifications.
For that I could create a new realtionship table where I add a new entry with every SQL-Insert or Update action.

Every log should contain several infos like the user-id, the data-object that was modified, maybe the before and after-value and the action itself (create, update, delete).

Should I write a custom action for that within every controller-function that adds, updates or deletes data?
Or should I look for a hook to manage it?

Thanks in advance!

jellix