We follow mutual respect rules, pretty much. In other words, we give plenty of notice unless it's an emergency (such as someone we know on TV, for example). We treat difficult child with the same respect we want him to learn to show to us and others. Generally, we negotiate. But we have multiple TVs, so unless there si a really good reason for difficult child 3 to watch what he wants on the main TV, he gets sent to watch his show elsewhere.
HOWEVER - it IS our TV and not his, we sometimes pull rank on this. He gts plenty of freedom to have his choice, so when we do get to say, "OK, this itme I insist," he's fairly good about it, as long as we give him time to transition. Ad breaks are a good time to change over TVs.
One really important rule though - because our main TV (the new, big one) is in the family room whcih is off the kitchen, we have "Cook's Privilege" which means, whatever the cook wants to watch, gets put on TV. The same rule applies in the car with the driver having the right to choose what gets played over the sound system. The driver is also the final arbitrator in games played in the car.
The interesting side of Cook's Privilege - if difficult child 3 is cooking something, he gets the right to choose! We found with the other kids, it was one more incentive for them to cook the evening meal sometimes.
Marg