A helpdesk should have a friendly face. For a physical helpdesk, the interior design should be pleasant and welcoming. A virtual helpdesk should be equally welcoming, which often means a design that uses soothing colors and readable fonts with the most commonly selected items at the top left of the first page.
The faces of the staff members also should be welcoming and friendly, as should their personalities. Some people have personalities that are suited for customer service; others don’t. That should be a consideration when hiring people for your staff. The tone set by the staff will reflect that set by the supervisor. A supervisor who yells at the staff will find staff yelling at customers.
A good-natured supervisor who can laugh and is always friendly will attract similar staff, who will reflect such an attitude with customers. It is easier to build a reputation for being friendly initially than to restore a bad reputation. In short, if you are the supervisor, be the friendly person you want your staff to be. Be a role model.