There is no certain way to play against the Najdorf since there are many ways Black can play(as is the case with all good defenses).
He's just asking for a recommendation...
6. h3 is interesting. It attempts to improve upon the slower but more normal 6. g3 (h3 idea is to play 7. g4)
6. Bg5 is the most theoretical. If you want to play an English attack then 6. Be3 and 6. f3 are both possible, each allowing little different things
What is a good way to play against the Najdorf? I am rated around 1650 so I am looking for a fairly simple system that gives me chances against players in the 1600-1800 range. I have been looking at the Adams attack, and the English attack. Any ideas about these two, and if possible some links to videos. Thanks