I never use PP healing items such as ethers or elixers.
I never use max revives.
I never use masterballs.
I used to never use TMs. Unlimited TMs are the greatest thing to ever happen.
None of the pokemon that are in my party are allowed to learn HM moves except for surf or waterfall so I get an HM slave out whenever I need it but put it back in the PC afterwards (Tropius).
All of my pokemon must be a gender that is the opposite of what they look like. (For example: Machamp, Slowbro/king, Weezing, Slaking, etc. must be female, while Bellossom, Clefable, Gardevoir, etc. must be male) I'm just weird like that lol..(Unless the IVs are good which is happening in my Black game so it's really really bothering me D; )
All of the pokeballs must match the pokemon's personality. (For example, Chansey goes in a heal ball, legendaries never go in timer/dusk balls)
No pokemon is allowed to faint while battling so I constantly soft-reset if one gets knocked out.
Unless I'm training low-leveled pokemon, no pokemon is allowed to share exp. since I want them to get the full amount and I soft-reset if it gets shared
Any nickname I give to my pokemon must be a normal noun without numbers or symbols and all pokemon must share the same name theme. (Platinum's theme was food names, Soul Silver's theme was things in a bathroom, and Black's theme is office supplies names).
I only catch the pokemon that I like unless I really need something from GTS so my pokedex is not that impressive...
Post-RBY/GSC I stopped using legendaries and they are now only meant for novelty.
After beating the Elite Four, I stop using my original pokemon party to battle so that I can save the exp for EV trained ones.
I always spam A while: an egg is hatching, I'm healing my pokemon, and after I throw a pokeball.