Nikon D200 and Lens 18-70mm having Auto Focus problem?

I have this Nikon D200 with Lens 18-70mm, unfortunately the auto focus is not working. I think the reason is with my camera settings. I'm new with this type of camera. Can anyone give me a good suggestion? Thanks.

Added (1). Yes, It was set to M/A but still its not focusing. And I was set also this to C S M…

Added (2). Yes, I was set already to C and S but still the same. This lens working with D90, D700. I don' think that my camera has a defect because I have two other lenses 18-55mm and 70-300mm and I can't see any problem with this.

Added (3). Thanks for your replied guys. This is my lens http://www.nikonusa.com/...IF-ED.html I don't know if it's G type or what. So you would suggest that I have to choose Aperture Priority Mode to make it f22? In this case my lens will be reset or something. Correct me if I'm wrong.

Check and see if the switch on the lens is set to the M/A position for auto focus with manual override. If its set at M it must be manually focused.

The switch on the body needs to be on C or S, the switch on the lens needs to be on m/a. If it still does not work the standard troubleshooting questions become relevant
- have you ever seen it working?
- when
- what have you done to it since?

The lens works with a D90 and D700.
The camera works with 18-55mm and 70-300mm.
The camera and lens are compatible according to the table.

My best guess is that the lens is not seating properly on the D200. Double check the connections on both the camera and lens. Make sure when you mount the lens that it clicks. If this isn't a G type lens, make sure it is set to the maximum f/stop (22?). I'm always having to reset my 50mm to 22.