When I was a kid, I was taught to 'narrate' the books I read - fiction, nonfiction, whatever - just 'tell it back in your own words' at a reasonable level of detail. That helped a ton with retaining most of what I read, as it trained me early on to remember it clearly. Don't really have to bother with explicit retention methods.

That, plus generally reading because there's specific information that I need to get out of the materials. Working on some project, need to know how to do something, find & read resources that help me do it.