Any lens with 24mm or less focal length would be ideal for landscape photography. Lenses with 18mm or less will provide wider perspective. Usually focal length range 10-15 mm are used by professional landscape photographers.

Its the Aperture that is denoted by f and it is also known as f stop.

The diffrence between both  is that f/1.4 lets you get more light to your image.

rather f/1.8 lets you get less light in your image.

More the aperture less the light and less the aperture more the light .

and one of the main use of it is the depth of the field.

Suppose you want your background to be blurred at a good rate then use as low apeature as you can.

Hope you will find it helpful.

The only thing you need to do so is a DSLR.

It also depends on  DSLR as to which type of AF technology  it uses or what are the diffrent types of focus points that the camera has.

And just automatically or manually focus your subject and you are ready to go.

By this you should be ok to focus on.

I usually format my cards before every shoot. Make sure you have at least two copies of the same saved as back up. Name a folder in camera itself and then start shooting. 

First of all that you should not try to disturb the audience. Always try to capture pictures from roaming around the walls of auditorium. Better to go with Telephoto for taking candid shots for stage subjects or from the audience.

Another thing is that you can use another camera for wide angle shots of entire stage or the audience.

You will need following things

1. A DSLR camera with a 200mm+ telephoto lens or a point and shoot camera that has an optical zoom capability.
2. A stable tripod.
3. Remote camera trigger (optional). If you do not have one, a timer in your camera will also work
4. Make sure you are in such a place where city lights don't affect your photo shoot. I would suggest going outside city area where you can find no lights, like Highways, Village etc. 

And following camera setting

Camera Mode: Set your camera mode to full Manual Mode.

ISO: Set your ISO to 100. If you have a point and shoot camera, see if you can find a menu setting to set your ISO to 100. Make sure “Auto ISO” is turned Off.

Aperture: Set your aperture to f/11.

Shutter Speed: Set your shutter speed to 1/125 

Lens Focus: Set your lens to manual focus (either through a switch on the lens or on the camera) and set your focus to infinity. Be careful while setting the focus to infinity, as some lenses allow focusing beyond infinity. If you do not have such a feature in your camera, then try setting your lens to the center of the infinity sign, then take a picture and see if it came out sharp by zooming in the rear LCD of the camera.

And voila, you will get this type of results

http://nisargpandya.com/portfolio/different-moods-of-moon/

Types of equipment that are needed to shoot long exposures

A tripod – this is a good piece of equipment to have in most instance, but is a critical piece of equipment for shooting long exposures. Make sure your camera is properly mounted on the tripod before you start shooting.

A camera – obviously you will need a camera, but many people assume you can only do this type of photography with an SLR. Some advanced point-and-shoot cameras can also do long exposures if they have a Shutter Priority function. Take a look in your camera’s manual to see if it has this function, you may be surprised.

Cable release – your camera will be on a tripod, so it should be very still, however, sometimes the action of pressing the shutter release button can cause the camera to move slightly and this movement can cause your image to blur very slightly. You may not notice this on the LCD screen, but when you open the image on your computer, it will be evident. I recommend getting a cable release (also called a remote trigger). It is simply a cable that attaches to your camera and acts as a shutter release button. Using a cable release means you can set up your camera, step away from the tripod and press the button without touching the camera. Cable releases can be wireless too. If you don’t have a cable release or don’t want to buy one, you could use your camera’s self-timer function to trigger the shutter.

Camera settings should be used

Shutter speed – depending on the light in your scene, your shutter time will need to be at least 10 to 15 seconds, or longer if necessary. If you are doing a seascape and the water is moving quickly, then a few seconds may be long enough to make the water look misty.

Aperture – you will want to have your aperture set at anywhere between f/8 and f/16. This again will be determined by how much light is in the scene and how long you want to expose for.

ISO – keep your ISO settings as low as possible, ISO 100 is what I use for long exposures.

It’s normally a good idea to shoot long exposures as the sun is setting, or just after sunset. My suggestion is to be on the scene an hour before sunset. That way you can test some shots, make sure your composition is good and be sure all your settings are correct.