logging / error management

[Olivier Zimmermann]

I am looking for information on two frequent programming topics:
* logging (on file, screen, with data, messages, errors...)
* error management (how to filter, how to structure error info, how to 
deal with it automatically...)

Do you have personal habits, advices, tools, principles... or know of 
any resources about it (design patterns, general or LV specific 
contributions or papers...) ?

oz