take a weak pokemon to the elite four
you train them
Train them............
if you want to level up your pokemon faster. give the pokemon you want to level up an exp share but it at the bottom of your pokemon list and battle and beat the elite4 in succession over and over until it is at the level you want it to be.
lucky egg
You get a lucky egg in about half way through the game. Also trading with someone.
cheat
YOU HAVE TO GET ALOT OF rare candy.
Its the same either way.
Try using Rare Candies for easy levelling. :)
Pokemon evolve when you level them up to a certain level, by trading them, by friendship, or by using stones.
you level it up 50
To level up pokemon quicker you must defeat higher leveled pokemon for one also if the pokemon your training was traded to you it will receive boosted experience points which help level up your pokemon even faster. If your pokemon holds a lucky egg item they will receive this kind of boost as well and if you give this to a pokemon that was traded to you it will receive even more boosted experience points.