Use Lucky Egg. Battle every trainer. The highest Pokemon you'll battle (first time around) is 54. My highest was 57 but I still had problems. And be sure to stock up on meds.
Mt. Silver or the Pokemon league
Other than secret bases the best spot is the Pokemon league.
the best Pokemon for the Pokemon league is definetly latios
The best place is probably in victory road or the route before it because of the high level Pokemon and if your asking there is no v.s seeker in Pokemon black an white
to obtain 5,ooo exp in Pokemon leaf green is to put a expirance share on the Pokemon you are training (best place to train is Pokemon league or victory road or clearun cave)
Mt. Silver or the Pokemon league
At the Pokemon league.
well, it depends. If you train it well, that pokemon wuill bethe best in your pokemon world.BUT I highly suggest you train black kyurem because its stronger than white kyurem.
Pokemon league :P
Victory Road.
The strongest Pokemon are in the Cerulean Cave which you only can get to after beating the Pokemon League. Pokemon here are anything from 45-60 in levels so bring an Escape rope just in case. If you haven´t beaten the League, Victory Road is your best bet.
victory road
Other than secret bases the best spot is the Pokemon league.
train it at the Pokemon league
The Pokemon League
it depends what level they are. if its not strong enough to battle, give it exp share and go to the league to battle with a stronger pokemon. or if its level is 30 - 40, battle at route 7 where it looks like this
The Pokemon league is proably the best place to train your Pokemon.If they are a low level give them an EXP share.OR you can train at Mt.silver and also if high enough battle red for a ton of xp