Any telephoto lens with focal length 200mm and above would be good. This is generic and affordable for most of amateur photographers. 

If you are willing to specialize in wildlife or willing to venture out in wildlife photography, can go for 150-600mm lens.

1 Best way to click pictures on a mobile phone is by using grid mode available on every cell phonenow you just have to put 9 things in those 9 boxes which will result in beautiful composition 

2. The angle from where click picture

1. Shooting with 50mm lens can let you shoot at aperture as wide as 1.8 but a 18-55mm will allow you to shoot only at 5.0 aperture 
2. This difference itself is a huge deal. This means you can have the advantage of having faster shutter . Imagine shooting handheld at 1/15s with aperture f5.0 and then at 1/125s with aperture f1.8. This can be significant in low light conditions.

A wedding i a magical event. It happens just once and so is it divine. It is the responsibility of the photographer to capture each and every sequence of this divine occassion in its true colour. It should not be all artificial, but it should have something that they do for the love of doing it. 

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.