One of my all-time-favorite philosophers is Daniel Dennett. He wrote many excellent books through which you can learn how to think better on specific topics and in general. But one of his books he focuses specifically on thinking:

Intuition Pumps and Other Tools for Thinking

https://www.amazon.com/Intuition-Pumps-Other-Tools-Thinking/...

I don't know that I can say I'm particularly good at this, but to the extent that I do have any original / good ideas, I think a big part of it is this:

1. Know at least a little bit, about a lot of stuff.

2. Know a lot about at least a few things.

3. Constantly trawl for new "stuff" (eg, read books, magazines, the web, watch documentaries, etc.)

4. Think about how to combine different bits of the "stuff" you have in your head. Take notes, write down lots of ideas, even if they're dumb at a first glance. Keep chewing on things, and eventually the penny drops and you see some connection between things that makes sense.

5. Related to that, and I don't do this well enough myself, is "spend a lot of time thinking about the kinds of problems people have".

I've read a few books on creativity / innovation / etc., but I'm not sure I can say any of them specifically helped, although a few of the ideas may have been useful without my being consciously aware of it. I read some of the Lateral Thinking book and I vaguely recall thinking it seemed somewhat useful. YMMV. https://en.wikipedia.org/wiki/Lateral_thinking

I also recommend Alan Kay's video series on "How To Invent The Future".

Part I: https://www.youtube.com/watch?v=id1WShzzMCQ

Part II: https://www.youtube.com/watch?v=1e8VZlPBx_0

Another thing: I think sometimes ideas come out that are "ahead of their time" and seemingly die on the vine, or just get left behind. But sometimes when the environment changes, those ideas become ripe to get re-invented. There's a book title Rethink that sorta deals with this idea. https://www.amazon.com/Rethink-Surprising-History-New-Ideas/...

Anyway, I think there's some value in reviewing "out of date" literature on various topics, and look for things that seemingly died, that may be ready for you to pick up and run with.

Finally, there's this book: https://www.amazon.com/Intuition-Pumps-Other-Tools-Thinking/...

I bought it a while back, but honestly haven't had time to get to it yet. But if seems like something that you might find interesting.

If you are interested in thought experiments, this book does a great job of providing you "tools for thinking". The book is called intuition pumps and other tools for thinking by Daniel Dennett.

https://www.amazon.com/Intuition-Pumps-Other-Tools-Thinking/...