The conventional wisdom is that you shouldn't try to think of startup ideas because it results in bad startup ideas. Instead, you should focus on solving problems. Many of the best startups have been created this way. Some examples include:
Dropbox
Drew Houston kept forgetting or losing thumb drives containing files he needed, He decided it would be great if his files could exist on his computer and the internet. Today, Dropbox is a public company worth nearly $8 Billion.
Stripe
The Collison brothers experienced how terrible it was to work with existing payment processing platforms as a developer. Their solution became one of the most valuable tech companies in the world and powers payments for millions of businesses around the world.
Zoom
Eric Yuan was fed up with complicated and unreliable video conferencing solutions for businesses. He created a simple, dependable and high quality product. Thanks to the quality of the software and some lucky timing, Zoom has grown to a $20 Billion company.
If there's a problem you have, and a solution that a) you can build and b) others are overlooking, you've found the sweet spot for a startup idea.
But what should you do if you haven't found that sweet spot? First, let's take a look at a different list of companies:
Slack
The Slack team was originally working on a multiplayer browser game called Glitch. While working on the game, they built an internal communication tool to make them more efficient. The game was a failure, but their internal tool was a different story.
Instagram
Instagram began as a location-based check-in app, similar to Foursquare, but with some additional photo sharing features. Nobody wanted to share their location on the app, but some users really loved the photo filters and sharing features.
Twitter
Twitter was born out of a pivot from a podcasting company called Odeo. When it was clear that project wasn't going to work, and the team was running out of money, Jack Dorsey thought it might be interesting to be able to send short messages to small groups of people, so they started working on that.
Twitch
Twitch started as Justin.tv, a startup where Justin Kan wore a camera on his baseball hat and livestreamed his life on the internet. Eventually, the founders opened their livestreaming technology up to other users, and observed that a small subset of users were sharing themselves playing videogames.
Each of these startups went on to become massively successful, and none of them started out with a great idea or even trying to solve a problem the founders had. Instead, what each of these examples has in common is that the founders were working on something that interested them, while keeping their eyes open for other ideas along the way.
If you don't have an idea that fits into the sweet spot described above, the next best thing is just to work on interesting projects. Working on projects introduces you to a whole host of new problems and ideas. Your job is to make sure you notice them and then choose the right ones.