How do you manage ideas, tasks, notes and other stuff?

Here's link to a previus thread https://news.ycombinator.com/item?id=8282569 I encountered.

But in the last 10 years a lot has changed, new apps, new tools, new research and new ideologies have surfaced. I'd like to know how you actually manage alot of things.

Personally being a 20 year founder I find this very hard and miss a lot of things because of unorganized management.