STEP 1: With Outlook 2007 open, click Tools -> Rules and Alerts.
STEP 2: Click New Rule.
STEP 3: Follow the "Rules Wizard" to create your rule. Click Next to continue.
STEP 4: At the end of the "Rules Wizard" name your rule. Ensure Turn on this rule is checked, then click Finish.
NOTE: By default the rule will only work on emails you receive after you have created your rule. If you would like to run the rule on existing messages, check Run this rule now on messages already in "Inbox".
Outlook 2007 will run the rule you have created until you turn it off or remove it. This rule will also be added to Outlook Web Access (OWA).