I am using Windows 7 and want to know how I can make USB bootable for installing MAC OS on my laptop.
Yumi is a very usefull program that can be downloaded from:
you can even consider using its multiboot feature its free and very easy to use step by step procedure is provided at the above link along with screen shots.
If you're using a PC laptop, which I assume you are, stop. Mac OS X was designed to run on very specific hardware--Apple hardware. If getting regular hardware to run OS X is a piece of cake, many people would have opted for regular laptops instead of the extortionately priced ones offered by Apple. I'm sure you've heard of Hackintoshes; custom made computers that run OS X. These machines are custom made with the exact hardware configurations that are supported by OS X. Even so, certain functions such as sleep mode or maybe even the intergrated soundcard on the motherboard won't work. Read this: http://lifehacker.com/5869731/can-i-hackintosh-my-laptop
How to create a bootable USB to install OS X
You can use your MacOS CD. If you have a .iso file it will be easy to transfer it onto a USB.
What is your source? If it is a .dmg file, you can simply use PowerISO or a similar tool to burn the image to a USB flash drive. If it is an .app file, you will need to extract the .dmg file from it first.