The fight over who gets or has to take the kids can get ugly and ruin any chance you have to work together. It helps if you have a schedule and stick to it as much as possible. Once you can do that you can be decent people and work together to build in flexibility but the default needs to be whoever is scheduled to have is who gets them with there is a conflict.

If you have family or friends in the area it helps. I would send my boys to their grandmother's for a week in the summer, it gave us a break and they got some grandma's house at the lake time. I personally always tried to take the high ground even though my ex did not always reciprocate. It was hard but I tried to remember that the example I set was more important than being fair and as much as I disliked her she was their mother and love her. Fair is for kids not parents.