"What are the key skills any good communicator should have?"

 First of all, a good communicator should be easy-going so he can express himself in a natural way. It wouldn't be good at all, if a communicator forced his speech; the audience would notice.

Also, a comminicator should have a good knowleadge of the language in order to avoid making mistakes. He should know when making pauses and when asking the audience to let them express an opinion.

Finally, he should know how to change the level of the voice to get the attention of the audience and to avoid people getting bored.