As a trained conflict resolution facilitator the number one biggest mistake I've seen (and have done when I was just getting started) is not fully listening to the complaint prior to rushing to resolution. (#2 above should be "2A. LISTEN to the issue, then 2B. concentrate on solution.") Often, the people involved need to feel heard...completely...before they will trust anyone trying to assist with a resolution. And, when listening fully, I cannot tell you how many times everyone realized the issue wasn't really the issue once the people involved had the opportunity to talk it through. So, the solution may never have fixed the problem if it was applied to the wrong issue.
Good luck everyone!