I have had this problem both in radio and tv. It helps if the actor or VO artist is experienced and is aware of this problem. It is terrible to get a novice in the booth who is totally unfamiliar with working in such an evironmentenvironment. I have had mixed responses from both experienced pros and new comers. What I find, apart from making sure their mouths are not too moist is to get the right distance to the mic after a few rehearsals to assess the actors voice and potential problems. But clicks will always be a hurdle in the process of recording and editing. Mic placement is silly, I don't understand why people say this.
Anyway, good luck with it and if I find anything else, I will file another answer.
