Appearance seems deceiving, that's my personal opinion. I thought it will be a simple task, but you never now when you actually did it.
Being a good moderator, in my opinion should be;
1. a good time keeper.
2. know what s/he doing in front with the material generally.
3. make an interactive situation.
4. directed participant question in relevant with the topic that being discuss.
5. ice breaking so loosing up the tense.
6. a good MC (master of ceremony) in the sense if you confident enough the audience will enjoy/love to watch what your doing.
7.
another additional ?.............. That what I've learn from my work here, and at that time choosing me as a moderator was quite surprising. Since i'm new.... so, lack of flying hour. But then they says there's always be the first time, and from that you'll learn and learn, and now somehow i enjoy it.