Lens hood: which lens hood can be used and what are the pros and cons?

I'm having a nikon D3000 with 18-55mm lens kit. I want to buy a lens hood but i have a very little idea about it.

So my questions is as follows.

1. Which lens hood is better the conical petal shaped or the circular lens hood

2. What is the difference in image when used with these two lens hoods

3. What are the pro and cons of these two lens hood

4. Can I invest in one lens hood to fit these kinds of lens AF-S nikkor 50mm f/1.4g and AF-S DX Nikkor 55-200mm f/4-5.6G VR

5. (most important) what is it that we have to look when we purchase a lens hood?

Thank you,

Sid

P.S Please be specific and no one liners…

P.P.S There's no P. P.S:-D

Each lens hood is specifically designed for certain focal lengths. Prime lens hoods are of a different design than zoom lenses.

Pedal shaped lens hoods come with specific zoom lenses. Many lenses do not have Pedal shaped lens hoods. My telephoto lenses have standard lens hoods.

You can look on the Nikon website to find the proper lens hood for your specific lenses

This is the proper lens hood for your 18-55 mm lens

http://www.nikonusa.com/...-Hood.html