This week I have learned how to create an object fallowing a path, and this object could be a camera as well, so I can set the path of the camera when I take a animation video.
1.A basic path
Firstly, draw a star path, and a sphere.

Select the sphere and go to tool bar on the top. Choose animation, constraints and path constraint. Then there is a dotted line comes out, pull it onto the star path.

save and rander it.
2. Camera pathThe way of setting camera is the same. Firstly, draw an object to shoot, and then draw a circle around it, at last draw a target camera and set the target to the object. Secondly, repeat the steps last animation.

3. Visit a room
At last, I create the path to visit a room.
Build a simple room, I have used the material editor make it easier to see, and one target light through the window as the sunshine and two omnis as nomal light, one on the top, other on the left to light the door side,

and draw the path by line on the floor in the top view. Set a free camera on it.

To create the animation, the important thing is setting the target , otherwise, it will only shoot one position all the time.
save it to AVI file,and render it.