My crontab (login as root; crontab -e) uses a cd command before running a local php, like this:
* * * * * cd /home/e-smith/files/ibays/sugarcrm/html; php -f cron.php > /dev/null 2>&1
However, I don't think I ever got local php execution working for Drupal, so my crontab line for that looks like this:
45 * * * * /usr/bin/wget -O - -q -t 1 --no-check-certificate https://mind.yourown.biz/cron.php?cron_key=jpGWAhDarVIgareyoukiddingpGgK54wMwSBsKRpZsY > /dev/null 2>&1