Many don't realize that they have the ability to add multiple cameras to a 3D composition. This makes experimentation easier as you can try out different camera moves without throwing the previous away. As you design, you can look through any camera you want with the 3D View Popup. 
You can trim the layer handles for the camera to control when a camera becomes active.
The gotcha is that only the Active Camera will render. Which one's active? The answer is it depends:
- If you have two overlapping cameras, the one on top of the layer stack takes precedence.
• If you want to edit between cameras, you can adjust the in and out points in the timeline. Then sequence the camera layers so you can cut between them.
From the new Adobe Press book – Motion Graphics with Adobe Creative Suite 5 Studio Techniques