A common problem for new administrators is setting up cron correctly. Depending on your host and operating system, you may not have access to cron or it may be difficult to configure. Thankfully, Drupal 7 provides automated cron functionality so that cron is always running after an installation.
The settings for cron can be found in the Site information settings within the Configuration section:
The automated cron system is triggered when a user visits your site after the cron interval has elapsed. The automated cron system is designed to work asynchronously in order to prevent performance from being impacted for the user who triggers cron. If you used Poormanscron (http://drupal.org/project/poormanscron) in Drupal 6, you will be very familiar with the Drupal 7 version.
If you prefer to use a true Unix-based cron system, simply change this setting to Never and then configure cron to run as usual.