HMy problem is, whenever I try to take photos in Shutter priority mode (with slow the shutter speed), I see the pictures only in Black and White or under exposed.
The shutter speed is only one of the three settings that you need to adjust to obtain a properly exposed image - have you also set the proper aperture and iso to achieve the correct exposure?
In manual mode you need to set all three of these settings to ensure you get the desired exposure. Even though shutter priority mode is semi-automatic you can't assume that the camera will compensate for all your mistakes. In shutter priority mode most cameras will automatically adjust the aperture to try and achieve the correct exposure - but they won't change the iso unless you have the camera set to auto iso. This can be a problem if you are using a slow lens (one that does not have a large aperture) because the camera can not open the aperture wide enough to allow sufficient light for proper exposure. - instead the camera will most likely flash a warning in the VF but still allow yyou to take an under-exposed shot. Even with a fast (1.4, 2 or 2.8 max aperture) you still may not be able to achieve proper exposure and may need to manually adjust the iso or increase the shutter speed (or set the camera to auto iso).
Also, remember that bad digital photos don't use up valuable film, you can just delete them and try again. By far the best way to learn how your camera works is to set it to manual and just play with the shutter, aperture and iso controls. Make small changes to the shutter speed and see how that alters the image, change it again and again and see how each change alters the resulting images. Then do the same with aperture - see how changing this will alter the depth of field (amount of the image that is in focus) and the iso.
lastly you mentioned shooting at night. This video tutorial focuses on shooting at night http://www.youtube.com/watch?v=LoPvsukr ... playnext=2
You might find the other 1on1 tutorial videos to be helpful. I certainly have.
I am learning photo graphee - see the results at www.danmarchant.com