I have never, ever trained a Pokemon to lv. 100 outside of PMD... unlike the Mystery Dungeon games, training is very time consuming, and gets dull quite easily. However, in Black, the battles seem to move faster, and are more interesting with the new Pokemon and fully animated sprites. So, I'm going to try my hardest to train my team to lv. 100. At the current moment, they're:

•ウォーグル: Level 70 ♂ Wargle, knows Shadow Claw, Brave Bird, Crush Claw, and Fly.
•Coast: Level 70 ♀ Daikenki, knows Surf, Revenge, Waterfall, and Shell Blade.
•Ivy: Level 69 ♀ Jalorda, knows Slam, Grass Mixer, Leaf Blade, and Giga Drain.
•Terra: Level 70 ♀ Waruvial, knows Dig, Strength, Crunch, and Earthquake.
•デンチュラ: Level 70 ♀ Denchura, knows ElecNet, Bug Buzz, Elecball, and Discharge.
•ビクティニ: Level 70 - Victini, knows Zen Headbutt, Flame Burst, Quick Attack, and Double Edge.

The highest level I've ever gotten a Pokemon to was 77, so I'm on my way.
Every day I battle in the Raimon sports arenas, where all of the Pokemon are around lv. 65. This used to really help with their training, but now that they're higher leveled, it's not as helpful, but still beneficial. Losing to Cheren about a gazillion times also surprisingly benefitted the team. I beat the Gamefreak guy on a daily basis, and his Lv. 75s provide a nice amount of exp. I managed to pull my team through the Elite 4 and champion when they were around Lv. 65, and they all went up at least one level; Victini went up three, I believe. With that team I've only defeated them once, but I plan on doing it again soon. And of course, I go about murdering strong wild Pokemon, particularly around Black City.