--Quoted from an old post.--
Under Linux
u can use the cron job like this :
login to the linux
using u r username and password
type crontab -e
it will open a vi editor
type the following
and close the file
00 06 * /usr/local/bin/php public_html/crontest.php
it will run the script at 6 am daily
the first parameter is the path of php interpreter and the next is the path of php file
hope this may help u.