if your up for it, use the pokewalker. each time Pokemon come off of it after 1000 steps, they level up. another way is the exp. share. you get it from Mr. Pokemon if you give him a scale from the red gyrados.
You battle all trainers and most of all train.
I suggest you try and find as many trainers as you can and use all your Pokemon in your party to defeat them when you can't find any more trainers look for wild Pokemon.
I recommend a level 100 lugia or ho-oh,a level 100 raiko,a level 100 arceus ,level 100 of any of the starters,level 100 scizor, and a level 100 of any Pokemon you choose
Just train your pokemon.
level 100.
You make a pokemon level X in pokemon HG or SS but a level X is a level 100 but it wont say level X for the level
train your pokemon up to level 80,90, or 100 and teach it TMs and HMs
Hold R before battle
level up Seedot to level 100 and the use a leaf stone on Nuzleef to get a Shiftry
You can't catch Level 100 Pokemon in any Pokemon game. The highest catching Level in Pokemon is Level 80. You need to raise your Pokemon to Level 100 or trade for a Level 100 Pokemon to get one. You can also challenge Level 100 Pokemon, but only in the organized challenges of the Pokemon games (i.e. Battle Tower, Trainer Tower).
There is no level 500 Pokemon. The highest level that a Pokemon can be is level 100.
Train your pokemon.
Level 100.
There's no room that has level 100 Pokemon.