How do you find a business idea to start with ?

One of my friend once told me "Its great that you started your business. If I were to start my venture, I do not know what would it be." The moot question is "Where to get that 100million or even 10 million $ idea? Answer is "Not many people know" Some people read trends and some consult astrology. Some ask around. There is no shortcut answer to it. In my opinion, ideas come because you observe. If you see someone gardening and observe the process, you will be tempted to get them some tool to make life easier. The point of entrepreneurship is all about observing and looking for improving things. If that is by developing new tools or using existing tools in innovative ways, it is entrepreneurship. So how do you get your idea? Observe, look for pain points. Look for things that you can change for better. Look where your expertise can help. Visualize how would people do things once they possess the knowledge you are imparting. Now look around and see what things you can change, create or improve. Is there anything that is not an opportunity?