The best way, in my opinion, is to bet everything in Final Jeopardy, and any Daily Doubles you may come across. If you don't know the answer, you should ask your friendly neighborhood search engine.
Also, buzz in for EVERY ANSWER so you can maximize your rewards. Also using a search engine, if necessary. It may take 3-5 games to earn $100,000. It did for me, but results may vary in terms of matches.
This will be done on Easy, since three answers are better than infinite.