You cant unless the scouts are down in your respective country, they watch you play and they think you should be called in for a trial.. all very unlikely scenarios due to the fact that you have to...
Well, you will need a level 85--100 pokemon. make sure all of your others are strong too. you should probobly get a bunch of hyper potions and pp restores.(max ethers, ethers,ect.)also, get a strong...