Through the past few busy weeks of mediations, I've accumulated an amalgam of observations, in no particular order:
Parties need to be heard, not just their lawyers;
I know lawyers are very busy (I was one not too long ago & remember!) but it helps to apply similar attention & prep to mediation as you would to trial, meaning, think through what elements you need to win your case, & do you have the evidence? Think through your opponent's case and what do you have to defeat it or respond to their allegations?
Don't automatically dismiss your opponent's claims-they just may have merit. I have seen on both sides the utter deflation upon realizing defeat of your client's contention, e.g. of having no contact with the other, refuted through phone records; or of working (not working) overtime, refuted by time records, computer or electronic log-ins, etc.; or day-in-life videos (ouch!)
Plaintiff lawyers: Get your client's med/psych records & wage loss or other damages records even if it is pre-lit; don't wait for them to be subpoenaed. You are trying to convince about your client's damages;
Defense lawyers: Get your client's personnel file, or other records to support defenses. "I think" bandied back & forth may not get too far;
If possible, talk to witnesses, get statements, or at least have phone access during mediation if the witness is critical to your position.
Don't shoot the messenger -yes, mediators are trained and used to being the recipient of people's anger & emotions, and in fact that is a normal part of the process; but it DOES help for everyone to hear & understand the others' side, and I/we know you don't like hearing it, neither does your opponent.
Have proper authority- not just how you value the case; Mediations have a way of showing people a different valuation of their case; we need all the right people there or accessible (being present is generally best);
Don't try to rush the process faster than it needs. Some people set a half day for a case filled with emotions on both sides & parties far apart. It CAN settle, but may need time to get everyone "there". Also, it's ok to complain to the mediator if you feel it's bogging down; but also be prepared that even if you/your client are ready, the other side may not yet be.
If possible, keep "briefs" "brief"..but pointed to important issues, drop the rhetoric -I encourage sharing whenever possible, & if necessary, send a separate "confidential" addendum to the mediator, or redact from your brief in order to send to opposing counsel. It DOES help!
Just some thoughts that may help you in preparing for your next mediation to be successful!