What can the average enthusiest do to get A+ HT?

I've read enogh posts over the years, and seen, heard, read about, installed, designed, sold, built, and experienced enough home theaters(including bassic surround systems, dedicated theaters, etc) to want to put the question out to the masses/fellow enthusiests out there. I'm currious to hear some of the more informed/experienced HT junkie's(like myself) input on to what they think they can pass on the the rest of the AV world at large would be, to help everyone truely maximize the Ht experience at home!
I've come to the conclussion from my years of experience around this stuff, that most(better than 99%) don't have a clue as to what they're dealing with, when aspiring to get even remotely approaching world class HT from their set up! Especially people experiencing this for the first, even going at it the second/third times!!!
Is it the gear? Is it the set up?..the acoustics?..the tweeks?...the calibration?...what? And if it's any and all of these things put together, can someone help spell it all out/break it all down in a realateively straight foreward manner, considering the variables people are likely dealing with/encountering (perhaps including budget/space), what options they should thus be considering, and specifics that need to be attacked/approached!?
I'm just currious if people who are serious about getting the best HT possible with-in their means/budgets(even at the ultra expensive and ambitious end) truelly want to know what it takes, and what they can do to get something truely special in their life time in respect to AV!..and that's assuming they want to mostly "go it alone", as opposed to hiring professinoals to do the job. We're talking about "home projects" and set up's here!...just to be clear.
Thanks for any input, commments, info, perspectives, etc.