Preparing for Jeopardy

Let's just say that someone took the test and met all of the qualifications. How would you recommend they study or brush up? James Holzhauer apparently did it by reading books of facts in the children's section of the library. Ken Jennings famously prepared flashcards on subjects that come up over and over again.

How would you prepare to play Jeopardy?
I'd need a Ken Jennings brain transplant. ;)

Seriously, that's the only way I could make it on that show.