I've been working on building startups for some time now, and I've seen many people trying to find great ideas to work on. People go to events, meetups, conferences, etc. to try to find the inspiration and, maybe, who knows, stumble upon a million dollar idea. But is this even possible?
Although I cannot rule out the possibility that some people might have built their fortune after looking for - and finding - a great idea, I think the right approach would be to focus on issues that people have and try to solve them. Great entrepreneurs that I have had the chance to meet and talk with often try to address a small issue that a few others have - sometimes even their own - and realize, by doing so, that many more people were looking for the same solution. And this creates a new market.
So, wouldn't it be better, and probably more efficient, to look for everyday problems and try to solve them? You can build a solution to such a problem by directly engaging with the people experiencing those issues. This way, you are already building your first client base. The people involved in the building process from the beginning are usually the best ambassadors for you and your product.
One way to assess if an idea can, eventually, have a more prominent and growing market size is to look for and evaluate future trends. For example, following recent technological breakthroughs, such as the Blockchain, it is clear to me that our society is moving quickly towards an increasing decentralization of services, from payments to smart contracts. Thus, trying to find issues that people have in this area has a higher chance of leading to a more significant and growing market. You can refer to my previous posts about the Blockchain if you want to know more about the decentralization trend.
An example of a successful entrepreneur who started out by trying to solve his own issue is the founder of Dropbox, Drew Houston. He used to commute to work every day by bus. Since it was quite a long commute, he used to work on the way home and he found it annoying to have to save his work on a memory stick in order to be able to transfer files from one computer to another. So, he started to work on a "cloud" solution to store his data so that he could access the files from anywhere there was an Internet connection. I guess it is worth stating that Dropbox is now worth more than $10B.
In conclusion, my point here is that wherever you search for new business opportunities, I would recommend looking for an expanding industry and trying to find solutions to problems that people have in that sector.