In San Diego County, any party with a child custody and/or visitation dispute is required to first attend mediation with the other party. This is done through Family Court Services (aka "FCS") at the courthouse.
During mediation, both parties will meet with a court-appointed mediator to discuss the child custody issues. Attorneys are not allowed to attend these mediation sessions.
To prepare for mediation, you should determine your specific requests. For example, instead of asking for "more time" with your child, be prepared to provide the mediator with a proposed schedule, outlining the dates and times you want to be with your child. If asking for a move away, be prepared to inform the mediator of where your child will be attending school, what area you will be residing in, what types of activities are available for your child, etc.
You also want to prepare your arguments against the other party's requests. Keep in mind, this should be done in a respectful way. The mediator will be watching your ability to co-parent, which is extremely important. Instead of referencing the children as "my children," use "our children" instead. This shows that you understand the importance of the relationship between your children and the other parent.