can any one tell me how to tweak apache in linux, please with details

i have linux server with 4gb and
root@host [~]# netstat -an ¦grep :80 ¦wc -l
518
root@host [~]# mysqladmin processlist ¦wc -l
7
root@host [~]#

that's not too much but i am getting issue like httpd goes to down after every some mins