@Crazy_Kate has some good points especially to not take sides unless it's totally appropriate...and in that case the member who is a "problem child" usually warrants being kicked. Fortunately our guild has been together for a very long time and we have developed mutual respect. One thing that tends to come up is Crypt difficulty setting. When this happens, I will post why the level is where it's at and how changing it would also change the number of lines and possible token rewards. I will put it up to members to comment and add their thoughts then we go with majority.
I post on the guild wall and/or chat regulary with positive comments on how we're doing in War and/or Crypt. I add suggestions for castles that could be focused on in a particular battle knowing the levels and abilites of various members. It may sound "high school" but I typically add something at end of my comments like "Go Team!" or "Great job! Keep it going!" or "Ok we lost this one but great effort!"
Some people don't do this, but when a player joins our guild they automatically get Verteran status. Since we have high level players I figure they have earned that status because they are typically level 80+. Then if someone isn't following established guild rules/guidelines I demote them to Member. This is their warning that they need to shape up because the next step is being kicked. Most will correct what's happening.
If I have something I need to address with one particular member I use private chat because the whole guild doesn't need to see a conversation best done with the individual. Sometime they go unanswered if they don't regularly chat.
We also talk about other things than the game and like to joke a lot. But since you were elected I'm guessing the guild members know you and will respect what you have to say. Good luck!