I myself made quite a bit, some of them being:
- never use Fast-travel - most cliche house rule I know... but I am a guy who always uses it in OB and even MW (I really can't play that game without coc spell)
- only use stuff I smith and enchant myself - my character is simply too proud to use other people's goods

- never stay away from home for too long after I adopt a kid
- order of playing quests decided by importance and character's (not mine) current mood... and while traveling, act like it (if quest is urgent, don't visit that fancy dungeon... if it ain't I'll think about it... If I want to piss someone (like Delphine) by being late, re-visit the place if needed

- whenever I find a Word Wall, gotta translate it and imagine my Dragonborn having a conversation with the person buried there... and why is the Word of Power important to that person... and later imagine a dragon in soul form explaining me the importance of the word
- if a Dragon is killed by side of the Word Wall, only unlock the Shout Word present there
- if I put on a Dragon Mask, act like the Dragon Priest (whose personality I predict by looking at place I found him in) took partial control of my character
- only level-up if there are stars in the sky or I am in a place where Dragon Magic is strong... chosen Perk and attribute sometimes decided by most recent quest
- the more Dragon Souls absorbed, the more dragonic my character has to act... that is, more ambitious and thirsty for power he is and I wouldn't do some quests the same way if I had 1 soul and when I have 20 souls absorbed... the character tries to resist it at start (so he turns good for a quest or two more) but later gives in