• Patience.
• Cynicism. If you don't have this, you can acquire it easily on the job, often without trying.
• A soothing voice, for when hysterical or enraged customers call.
• Patience.
• A sense of humor.
• Coffee.
• Nerf weapons for blowing off stress.
• Hard liquor, ditto.
• Patience.
• The ability to keep in the back of your mind that, no matter how bad it may seem, it's not your server that's broken.

Computer skills may also come in handy.