Mostly, I aim to fill out the stars on the Trainer Card, e.g. mastering contests, filling out the 'Dex, etc. The Pokédex is definitely a huge one for me, though I don't worry so much about Battle Frontier stuff (since I'm not great at it and messing up once sets you back hours worth of progress). Other than that, I make sure to finish out all of the sidequests for each game (of course), then do re-runs with some of my cartridges in which I don't have large amounts of 'Dex completion and the like.
Challenge runs are increasingly prominent for me - currently I'm doing a team locked at three members (Roserade/Drifloon/Mamoswine and nothing else allowed to battle) in Platinum after a devastating FireRed Nuzlocke failure.
Right now, I'm also working on bumping every Pokémon I ever beat the storyline with to level 100 and storing them in my Black file - I'm almost all of the way through two boxes worth. Good times.
Challenge runs are increasingly prominent for me - currently I'm doing a team locked at three members (Roserade/Drifloon/Mamoswine and nothing else allowed to battle) in Platinum after a devastating FireRed Nuzlocke failure.
Right now, I'm also working on bumping every Pokémon I ever beat the storyline with to level 100 and storing them in my Black file - I'm almost all of the way through two boxes worth. Good times.