how can I see what a camera sees

1) Use the 2 split layout. This way you keep the sceneview and game view.

2) Select the camera and use Align with view to place the game camera exactly like the scene view's camera

 

A simple script which just rotates to look at a target point goes like this:
Just add the script to the camera or light which should follow some transform.
After adding the script, simply assign the target to be the target you want the camera or light to look towards.

Code (csharp):

1.  
2. var target : Transform;
3. function Update ()
4. {
5. † if (target)
6. †{
7. † † var direction = target.position - transform.position;
8. † † transform.rotation = Quaternion.LookRotation (direction);
9. †}
10. }
11.