Just put it in the first slot so it will be the one that comes out when you throw the pokeball, and keep your strongest Pokemon in the other slots so if it faints then you can get out of the battle quickly. Another way without battling is to put them in the daycare and ride your bike around in circles. (tip: you can buy some repel to keep track of your steps) That will get their level up.
train it
I am not too sure.
Have a Pokemon that was traded to you then have the Pokemon hold a lucky egg and start battling your Pokemon will level up very quickly.
you have to train for a month or give a bunch of rare candies
train... train...TRAIN...
Train it as you train all pokemon.
you just catch and train alot of pokemon.Hope it helped!
You an train Pokemon in the grass
Train at victory road
Pokemon LevelBattling with the trainers or using too much Rare Candys also u can give the Pokemon u want to train an exp share.also put the Pokemon u wanna train in front then battle.on the first turn switch it to ur strongest Pokemon then kill the Pokemon.they will both get exp. rewpeat as many times as liked.thanx
you train Pokemon by letting it battle other Pokemon or you can feed it rare candies.
Train, train and train!