The standard start/stop scripts are located in /etc/init.d or for older linux versions /etc/rc.d/init.d.
Stop apache: /etc/init.d/httpd stop
Start apache: /etc/init.d/httpd start
If you run cPanel there is a restart script located at /scripts/restartsrv.
To restart Apache run /scripts/restartsrv httpd
If you have an /admin folder apache can be restarted by running /admin/res httpd