tailing log files to watch them is a good thing as it keeps you updated in real time. This is an essential and greatly useful task for a systems admin. This tells you what is happening now.
tail -f /path/to/file.log
Most log files are in /var/log. Apache / Cpanel logs are not here however.
/var/log/secure contains FTP/SSH login info (login failure messages)
/var/log/cron = cron logs.
/var/log dmesg = startup logs.
/var/log/httpd = apache logs, there's a symlink here for the correct log file (/usr/local/apache/logs)
/usr/local/cpanel/logs = cpanel logs.
/var/log/exim_mainlog = cpanel's main EXIM log. Verbose logs.
/var/log/lfd.log = Login Failure log
Logs and Statuses
access_log contains apache server over IPs
domain logs are like access logs, but for domains.
log warn levels: notice = purely informational. warning = technically incorrect, but shouldn't effect anything. error message = errors.