I believe that we all have ideas constantly, but we have generally trained ourselves to ignore them. How often have you had a fleeting "it would be great if..." thought that just passed through your mind never to be thought of again?
In practice, after years of doing this, I add about 5-10 items to the list every day. Every so often I go through and extract the most promising ones to another list for further contemplation.
As a result, I have more than enough ideas for a lifetime. When I'm looking for a new project, I scan through the list and almost always spot an idea that I find particularly appealing in the moment.
1. Random ideas that come from reading, browsing, coding - like https://eamag.me/2024/HackerNews-Prediction-Evaluator#why
2. Have some big goal in mind and think about missing things that have to be built to achieve it - like https://eamag.me/2024/Automated-Paper-Classification#motivat...
There are imo two general paths: opportunistic (in a positive sense), and inspirational. The former maps to 'resourceful' mindsets, the latter to 'creative'. Since you are asking this question, the assumption is that you are not a naturally creative type, so work on the opportunistic angle.