Assuming you've root access, we need more details:
1. OS and distro;
2. Apache/IIS/Other WebServer version;
3. PHP version;
4. MySql version;
5. Show us the result of the 'top' command;
6. Show us the my.cof file (exclude your password);
7. Execute this command from the shell: 'mysqlreport --all -tab /statistics.txt' and paste here infos inside statistics.txt;
8. Show us a phpinfo page;
9. Show us these infos about apache conf:
KeepAlive
MaxKeepAliveRequests
KeepAliveTimeout
MinSpareServers
MaxSpareServers
StartServers
MaxClients
Maxrequestsperchild
banned,