I only have a few rules that I don't break, and some have already been mentioned by others:
1) Always lye to water/liquid.
2) Lye water in #5 plastic pitchers - and I prefer deep pitchers to reduce splashing problems.
3) Pets (I don't have children) locked out of the kitchen until I've finished soaping and have put everything away and wiped down the counters and mopped the floors with a vinegar solution. My husband is welcome, but I'll run him out too if he distracts me
4) Goggles and nitrile gloves anytime I'm dealing with lye solution or raw soap - and I change gloves before I handle my goggles. I learned this one the hard way...measured out my lye and made my lye solution and took my goggles off with my gloves still on. When I put the goggles back on to mix the lye-water into my oils, the outside of my eyebrow on one eye started burning and stinging. I ended up with a crescent shaped lye burn on my rt eyebrow/cheek from where I apparently transferred lye to my goggles via my gloves!! No biggie, but I'm more careful now.
Other than these, I don't really have any rules. I usually soap in a T-shirt and shorts wearing flip-flops or barefoot...and I will be the first to say that I knew better if I ever get a serious injury. But it's HOT down here, and the occasional lye-burn isn't enough to make me suit up like a bee-keeper - yet while I'm willing to take the chance, I certainly don't recommend anyone else to do so. This is just my personal choice.
And if I'm trying a new recipe, I use the soap after a week's cure. I know it won't be at its best, but I'll have an idea if it's what I was attempting to achieve.
I'm also avid about 'mise en place' ...a culinary term for what another poster mentioned about having everything in place before you start. While my first couple of lye solutions are cooling down, I heat up my pre-measured hard oils and mix my fragrance in with the soft oils along with my additives.