1. cleanliness;
2. excellent ingredients;
3. temp control.
re: 1, I am anal about cleanliness. If anything touches something I already sanitized, I sanitize it again.
re: 2, I buy excellent ingredients and keep them properly stored. Under this, I chalk up water. The water where I live now is incredible. Same with the honey, so I carbonate with honey when I can and do beers with honey as an ingredient,if it makes sense.
re: 3, while I have no capability right now to have a fridge and a temp controller, I do have a room that stays stable, temp-wise, throughout the year.
Below those three, I'd put things like equipment. Having easy to clean equipment sure makes brew day easier, and thus makes me want to brew more often.