Audit trail ?

Hello.

I must have audit trail of all insert/update/delete on several table. I have
several questions regarding that:

1. Is it better to have one audit trail table that collects
insert/update/delete of all audited tables, or it is better to have separate
audit trail table for every audited table ?
2. To use triggers or rules ? Example for both ?
3. Could someone give me an example of a successfull audit trail solution ?

I'm running on lack of time, so any help would be precious...

Thanks.