Open a replay try to stop it at the start than you move the camera to your fav startposition and press "P" replay is running now while the replay is running move your camera and everytime you got a good position or a good place where the camera should stay at press "K" (saves the keyframe) after you pressed switch to another position press "K" again now the camera will move from the 1. place where you pressed "K" to the 2.place where you pressed "K" again you can press "K" unlimited at every place you want the camera will follow those spots where you pressed "K"
IF you press "K" at a spot and you stay there for 200 frames the Camera will stay for 200frames there , you can stay there longer or shorter however you want.

To delete the keyframes press "I" that will delete every Keyframe you made in the replay and you can start keyframing again if the old keyframing wasnt good enought for you.

Hope that helped