Q: My ex and I have three lovely children. As a mediator, can you suggest how we keep from putting the children in the middle and making them feel like pawns, as I have seen happen with some of our friends?    

Excellent question and one that goes far beyond the scope of this short answer. That having been said here goes:  

1.  Avoid any temptation to make derogatory comments about the other parent. 
Children are amazingly intuitive and smart creatures at any age, and are capable of making their own assessments if they are not prompted to take sides. 

2.  Kids are masters at the game of playing one parent against the other and often do it unconsciously. 
Don’t engage! Communicate clearly with the other parent about plans, permissions, homework, medications, etc. and avoid contradicting the other unless it is a matter of health or safety. Don’t try to out-purchase or out-play each other!

3.  Recognize that children often experience about a three-day behavior shift after spending time with either parent.
Try to insure consistency, be respectful of their private time with the other parent, and don’t pump them for information or share your own feelings of anger, frustration, distrust, jealousy or information about financial issues.   

Differences in parenting style are common and may have been a catalyst in the divorce. Don’t expect those to disappear. When issues arise, remember to ask questions that don’t imply fault, ask open ended questions to determine what interests may be underlying the problem, and don’t be afraid to seek joint counseling on co-parenting. Set clear boundaries with your children to let them know that you don’t really need/want to know what the other parent is doing. This helps them set healthy boundaries that will serve them well in developing their own friendships and relationships later in life.