Whenever I play any pokemon game, my first tendency is to pick the grass starter.
I used to get a full team before gym 3 when i was younger, but these days I normally keep 2 pokemon until the fifth or sixth gym (resulting in ridiculously overlevelled Pokémon. I'm looking at you, my level 29 bayleef before beating Falkner in Pokémon Crystal)
Apart from that, I enjoy going out of the traditional way of completing the game, i.e beating Erika, Koga, and Blaine before challenging Lt. Surge in Fire Red, completing Mahogany town before Cianwood City in Pokemon Crystal, etc.
Lastly, I almost can never bear nuzlocke deaths. "That Pokemon died from Poison outside the battle, it doesn't count!" "It died due to confusion, it doesn't count!" "Using one revive won't matter. Just one. Just one..." And stuff like that.