Having said that you ought to read logs it's probably worth mentioning how to configure what logs are kept. Most programs under Unix log via syslog. This can be configured with the file /etc/syslog.conf.
This file consists of two columns. The first column is of the form process.log_level and the second column tells syslog where to output the logs. You can use wildcards in the first column, so
*.* /var/log/all
Creates a logfile called /var/log/all that has everything in it.
mail.* /var/log/maillog
Send all mail logs to /var/log/maillog.
``man syslog.conf'' give more information on the file. It is also worth knowing that syslog can send logs to a remote computer, for example:
*.* @eddie.cipe
Would send everything to the computer eddie.cipe. Assuming eddie was running syslog the logs would be processed by it as if they were it's own.