1. If a pokemon faints, you must release it, signifying it's "death"
2. You can only capture the first pokemon you encounter in an area, and only one pokemon per area (no catching two of the first one you see)
For some playing the game, whiting out (all pokemon fainting in one battle) means game over. I'm not going to do that. Some people even play by the extreme rules, which I will cover
3. No items that heal
4. No Pokemon Centers
5. Set limit for amount of pokeballs you can buy per mart
6. No legendaries (I will probably use this rule)
7. No flame during battle
8. Set battle style to "set" instead of "shift". This disallows you from getting a freebie pokemon swap from the opponents pokemon fainting. This one I may use as well.
With the extended rules, your pokemon's health is eternal. When your pokemon takes damage, it is permanently damaged.
I could not do that, especially with a game I have not played yet. A common unspoken rule is that you nickname all of your pokemon. This is new to me, as I never really bothered to nickname pokemon as a child, due to me not being creative enough