The guy in the kiloude city pokecenter will hint you to how many ivs you have.
The IV-Checker will say ''Stats like those... They simply can't be beat! That's how I judge it.'' when your Pokémon has 31 IV's in a stat. He'll always say it after he tells you about the stats.
As to get them you have to give a Pokemon with 6iv a destiny knot and breed it so it can pass down atleast 5 ivs. To get that 6th iv you have to get lucky. Of course you don't really need to use the destiny knot trick but it becomes a LOT easier if you do.