I don't remember making any rules in my play as a child. In fact, I sort of have an aversion to rules. I played a lot by myself as a child, so there really wasn't any need for rules.
I have some rules for my apartment:
1. NOBODY except me is allowed anywhere near my DVD, CD, and LP collections, and 78 rpm records are handled ONLY by me (because 78s break very easily and are virtually irreplaceable in this day and age). I have a lot of very rare CDs, LPs, and DVDs, so I need rules when it comes to this.
2. Nobody except my family is allowed in my bedroom. Consequently, I allow it to get messy.
3. Anyone can sit anywhere they like in the living room. They don't need to ask.
4. The center chair with my dining room table is mine alone.
5. Enter the bathroom at your own risk. (It is not always at its best.) You also don't have to ask permission to enter it.
6. It is not permissible to touch my computer without my supervision. (If something happened to it, I would have no idea how to get it working again.)