Well, you can use action replay to get rare candies or you can put it first in your party and go battle but immidiantly switch it out during battle and it will get a share of points.
There isn't really a specific time to how fast your Pokemon level up. The younger the Pokemon(smaller the level) the faster they level up. also battles the Pokemon is in give it more experience. so if you wanted to level up a oddish and you gave it exp. share it would get less experience than if it was the first in the party/ battled the enemy Pokemon itself. If you trade what you want to train to a friend and give the Pokemon a lucky egg it well level up really quickly, only a few hours to wait and it will be level 100 in no time.
cheat
if you have already beaten the elite four than you can keep going there and training you Pokemon there. hope this helpz
Get the Exp. Share and give it to the Pokemon you want to level up. Be sure to put in your first slot. When you find a battle substitute your Pokemon right away for one that is really good. Then make your opponent faint. Your Pokemon should earn alot of Exp. points. It will then level up!
try rare candies
To get a Pokemon level up quickly is to have a Pokemon hold exp. Share and then just battle a bunch of trainers or wild Pokemon.
Dark Cry? There is no such game. I belive you mean how to level up the Pokemon DARKRAI. Correct?
If you have the Exp.share give it to your Pokemon that you want to level up then go to beat the elite four and the campion
In my opinion, I always goto the elite four (aftergame) and replay them. You can also goto the east side of Unova and fight wild pokemon.
The Pokemon magikarp evolves into gyriados at level 20 just put an exp share on the magikarp to hold and the levels will shoot up really fast
By giving it rare candies :)
Easy really there are (or were) certain accounts people made for the exact purpose to level your Pokemon. First you would find tab that said "battle computer playor" enter thbase name and type of Pokemon you would like to level up. It would be like "Zedjarock", or "Zedjalightning", etc. some more effective than other. >_<