My AH and I just fired our mediator and hired a new one. Our first mediator wasn't strong enough in her ability to lead us through the forest of divorce. We both felt that, and we were coming out of meetings with her feeling angry and confused. The new mediator is much better. Make sure you are going with someone who you feel really good about and who is sharp, organized, and very competent. Our first mediator was not, and that has caused us grief, a waste of time and several thousand dollars!
A good mediator should provide you with an agenda prior to each session so that you know *exactly* what you will be covering in your two hours.
My attorney's advice to me was to go into the meetings like I am attending a business function. Put my business hat on, bring my brain and big girl pants and leave my emotional, hurt wife self at home. Eat a solid breakfast with protein and try to be rested. Make the mediation appointments for earlier in the day, when I am fresh. I scheduled mediation sessions so that I could go to my counseling appt that same day or the next day. That way I could take my emotional stuff into counseling and process it there when it's fresh.