There are certain things they have a burning desire to get off their chest. Similarly, there may be things you want to get off your chest. Both sides need to be afforded this opportunity. It will also bleed off some of the emotions that are often part of a dispute. Remember, they won't listen to you if you won't listen to them.
Negotiation is the art of compromise.
Be prepared to compromise. Be prepared to back off positions that are taken only for the purpose of gaining leverage. It is hard to be viewed as negotiating in good faith if one refuses to pay money that is acknowledged as due. Fix the damages. If you can't agree on whom should pay, try to agree on how much would be paid if anyone pays at all.