Rule #1 - Good tunes are necessary. I pick what gets played and nobody gets to complain. Whether it's Led Zeppelin, John Coltrane, Philip Glass, Sigur Ros or Talib Kweli. You complain about my music selection and you are kicked out of the brew space.
Rule #2 - RDWHAHB - I had limited myself to not drinking until after the boil was under way, but I've found that I generally stay busy enough on a brew day (cleaning, measuring and prepping boil additions, explaining the brew process to my dad for the millionth time, taking notes) that I don't drink fast enough to lose track of what I'm doing anyway. So, I have a beer when I feel like having a beer, end of story.
Rule #3 - Wear a brewing/beer related t-shirt. It lets people know what I'm doing, in case they couldn't tell.
Rule #4 - Plan the next 17 brew days and recipes. I think I have recipes picked for my next 5 or 6 years of brewing at this point.
Rule #5 - Learn something to better understand the brewing process. Think about and figure out something about how the brew day progressed and how it may have effected the final outcome. Maybe a grain used for the first time absorbed more/less water than other grains in the mash, ended up more/less powdery/flour-like after being crushed, added more/less color than expected. Maybe the yeast in the starter flocculated more/less than other previous yeasts. Maybe the OG was higher/lower than expected. Notice these things and try to figure out why they happened. You'll never learn the answers, if you never ask the questions.
Rule #6 - Take pictures of the brew day to post online and make friends jealous, especially the friends whose SWMBO won't let them get into brewing.