- Don't steal any item owned by another, except books. Books are my vice.
(Reason: if I use TFH and see a dozen owners when my mouse hovers over my saltrice, I am bothered by it.)

- Since I use the Morrowind Crafting mod: Only wear stuff that I crafted myself. I may make an exception for one or two simple armor pieces made of Netch Leather that I acquire early on, because it's annoying to have to wait for ages until I can craft my own netch leather shield. It's way more interesting if you have to craft your own arrows and stuff.

- All merchants in my game have extreme speechcraft (no easy bribing) and extreme mercantile. They give me crappy prices for my goods.

- Alchemy: I've a new set of rules for that. At "novice" skill level (<15), I can only use an apprentice mortar+pestle. At "apprentice" (skill level 15-30), I can use full apprentice gear. At "journeyman" (skill level 30-45), I can use full journeyman gear. Skill level 45-60 means master gear. Skill level >=60 means grandmaster gear.
(Reason: Despite the inhospitable merchants, I could make too much money by stealing my grandmaster mortar+pestle from Naraya in White Haven as a lowbie character, and I didn't like it.)

- Speaking of merchants: I don't like the Creeper of the Mudcrab merchant very much anyway, so I just ignored them so far. My inhospitable merchants have large amounts of money anyway.

- Try not to kill NPCs. You'd be surprised how many differences a Calm Humanoid + some Speechcrafting treatment can fix.

- I'm using Better Bodies (mature version), and now I stopped stealing clothes from dead NPCs. I may have had to defend myself against them, but at least I left them some decency. I do steal their armors, weapons and jewelery though.

- I use GCD and don't have a character build that will result in an extremely durable character. Fragility = fun.

Ditto, mostly it just takes forever if you try boosting a couple skills a lot, and don't feel like you are getting anywhere.

Avoid swimming in the water if possible.

Avoid selling self-made potions, unless i'm seriously in need of some cash.

Never kill a citizen unless attacked, or part of a quest, in which case i 'taunt' them till they attack me.

Try not to use the console unless debugging, or a glitch happens.

Don't use enchantments of pre-enchanted items weapons/Armors.

Don't use/carry scrolls/potions unless extreme emergency.

Whenever i finish stashing my stuff, don't carry armor/weapons (except boots of blinding speed)

Never stash/sell damaged equipment.

Only do enchanting at my location of residence.

Don't level any 1 skill more than 10 per level.

Don't skip quest steps.

I don't buy into most of the "realism" aspects, because I find having to eat three meals a day to just be too much of a distraction. I often get a good night's sleep though. I also save before going into any combat, and if I die I have to first go into that combat (because hey, I thought I could win), and either win or safely retreat. Which does mean I sometimes go into a fight multiple times with the sole intention of just surviving long enough to run away

when i go to sleep in a tavern i take off clothes. i even have nightdresses with me.
i build in nearly 400 water objects for bathing, washing, drinking and so hop in a bathtub everytime i'm in a tavern that offers one. i have a towel with me.
i take off clothes for swimming. if i just swim for refreshing i leave my clothes at the beach.
no alcohol for me, so no greef, mazte, shein or all the other stuff.
if there are plugins that offer stuff to find for free and without challenging i make a shop that sells it.
if i shall get an quest-item where killing an innocent npc is involved, i built in the opportunities to get it without fight in exchange for another item of the same value and that includes some non-kill challenge (sanguine items or auriels bow).
i try to eat before i go to sleep and wake up but often forget that.
i don't run in buildings.
i change clothes from time to time.
no self-enchanting.
no console.