I have a CentOS 5.8-based VPS and for 4 months I have been facing random system hangs every 2 or 3 days; then I need to reset the VPS through its control panel. How and where can I start debugging those hangs?
this link is usefull concerning logs on centos : http://www.centos.org/docs/5/html/Deployment_Guide-en-US/ch-logfiles.html
read /var/logs/messages for general stuff look for access_log / error_log in apache directory / virtualhost for your website
you should read them all and try to get a clue to what is going wrong look in /var/log/messages and do some research on what you found and add it to your question so people may have more info to help you
note that logs have to be read from bottom to top as the last entries contains the last (error) data
don't post everything if the file is too big , just the last 20 lines for example will be a good start (ex.