QoS help needed.

Anyone know how to set up QoS on a switch.  I need to give priority to Voice over data for my VoIP system.  The VoIP will be on a VLAN too.  I set up the VLAN with no problems.  Now I just want to make sure voice gets priority over data on the same switch. I am using a Dell Powerconnect 3324.

Thanks,

aircox23