how to start a small business after school life ..which business can i prefer?

I agree with everything Steve said Gangadharan. The only thing I'll add is you first have to find out what you're passionate about. Education, the environment, sports, music, politics, whatever it is find something you love and want to be involved in and build your business ideas around that and then get to work!

Best of luck -

There's no reason you can't do both: start a small business while continuing your education. In today's world, having some college is a real plus with prospective employers so I wouldn't recommend you leave school if you can avoid it.

I tell people to spend the first 10-15 years of their adult life becoming an expert and then the rest of their lives selling that expertise.

To start a business you just need an idea, preferably one in which you have lots of experience. Think about areas where your friends and family ask you for advice or a product you personally would like to use.

Once you have an idea, put together a test to see if you can find others who would be interested in buying it. For example, before writing a book on a favorite topic, set up a web page with details on the book as if it's already completed, and see how many people ask to learn more. Or create a flyer for a local bulletin board with a phone number and see how many call.

A product test looks like this: 1) I believe [something]; 2) to test this belief, I will [run a test.] 3) I'll know the test is successful if I get [some result.] In my earlier example, 1) I believe people would buy my book on product management; 2) to test this belief, I will set up a landing page for the book with a high-level outline. 3) I'll know the idea has merit if I can get 100 people to preorder the book.

In the end, your goal should never only be money. There are plenty of low-wage jobs that pay money. What you want is to create a business that you can enjoy that pays your bills. Your goal is to create satisfied customers who pay you for your product.