Well, certainly not listening to opinions from other people. It has to be individual opinion of what's 'good' that matters, or we end up with a prescribed catechism of ins and outs, leading to much the mess that seems to be what the hip custodians of contemporary photography seek to perpetuate.
If you spend enough time reading about the so-called great modern snappers, you might be forgiven for thinking that mediocrity rules and that subject (even at the cost of technical quality) is all important, especially subject that embraces the more seedy aspects of today's living or, better still, the painfully banal. And if it's big, it's irrefutably better. Apparently.
It's easy to mock some of the old greats of the immediate past - poor old St Ansel comes to mind - and by naming him in that manner perhaps I'm as guilty as the next, but though I think his work has been over exposed in media terms, I still have great respect for what he managed to get out of film and a sheet of paper. Like it or not, his photography of the wilderness is quite majestic and technically brilliant and, at the very least, that earns him the accolade of producer of good photography.
There are many other photographers who produce work, within their own field of interest, that leaves one quite impressed and somewhat intimidated by the display of photographic pyrotechnics that they can pull out of a box with a lens stuck in the front. And by pyrotechnics I refer not just to the technical aspects of craft, but as importantly, the ability some have to put the viewer unequivocally right into the middle of the experience. That's some power!
So no rules, just results.
Rob C