Be on time.
Plan ahead. Especially in urban areas, traffic is no excuse for keeping your kids waiting, as bad traffic is often predictable. Chronic lateness is not only impolite, it can eventually lead to a judge reducing the amount of time you get to spend with your children.
Stick to the plan.
If you've already set a meeting place, don't call at the last minute to change it. Keep in mind that change is stressful, especially at the last minute.
Don't bring up issues like child support or co-parenting issues.
Save these conversations for a time when the children aren't present.
Know what you need and have it with you. No one likes to scramble around looking for soccer cleats or homework, but when transitioning between households, it becomes extra stressful for the children.
Don't bring a friend or a date.
It's uncomfortable for the kids, and it's not necessary. Many judges will tell you that until you're serious enough to marry, there is no need to introduce a new romantic interest to the children.
If domestic violence is an issue, do bring a third party who can be a witness, a deterrent, or intervene if necessary.
Try to bring someone the kids are comfortable with, such as another family member or trusted family friend. Save the police for true emergencies.
Keep the kids out of it.
Even if you're sitting in the car waiting for what feels like the millionth time, or your ex shows up without a coat for your child in the middle of winter, do not make comments. No "Isn't that just like your father?", or "Well, I see Mom is late ... again!" It's bad for the children, and it's not going to reflect well on you in court either.
Don't send messages through the kids.
The same goes for handing over child support checks, even if they're in an envelope. You're adults. You need to find a way to speak to each other that doesn't involve putting the child in the middle.
If your ex doesn't follow Rules 1 and 2, be the bigger person and don't give in to the urge to be stubborn. Go to the store instead of meeting at the house. Meet your ex halfway if he or she is stuck in traffic. You'll be teaching your child valuable lessons in giving grace, and as an added bonus, a court may reward your generosity of spirit if you end up back in court.