Empathy is the big one, as is acknowledging and playing the positions of power. As help desk, it’s natural that you’re going to have to escalate many issues, either to a more senior member of your group or to the on-site field techs.
If you’re unable to resolve issues yourself, whether in person or on the phone, and you have to escalate, you let them know that, and that you’ll make sure that it gets taken care of right away.
They may get snippy and bark back that they “ALREADY TRIED THAT” with every suggestion you make. In those cases, you may just have to escalate right away, even if they didn’t actually “already try that.” Although you’re expected to maintain a professional demeanor, that doesn’t mean that you have to accept abusive behavior either.
Although how you handle it will be different with each case, the idea is to let the person know that they’re in your hands and you care about their issue, even if it’s minor in the grand scheme of things. The issue isn’t minor to them.
Case in point: user can’t print, because the desktop printer in their office isn’t responding, despite being surrounded by multiple networked printers a short walk away in any direction. The wrong answer is to merely suggest they print to one of those printers, and just be done with the call. The right answer is to ask for other surrounding details, because this may be, for example, a social worker or counselor who needs to print a confidential report right away for an IEP meeting, and having that information sitting out in the open is not only bad juju, but could also be illegal.
If you don’t know the answer, say so and say you’ll go ask (and make sure you do). If the confrontation gets worse, try to hand it off to a more senior member (again, there’s a line between professional service and taking abuse). But overall remember that they’re not calling just to be a jerk to you.
There’s a reason they’re mad, and it may have absolutely nothing to do with you, so try to find what that reason is and put yourself in a situation to where that’s happening to you and how you’d feel.