>>14726951I explained this a couple threads ago. Included image covers most of it, some minor things have changed. Essentially:
Power Items you get post-game are amazing. Use them to guarantee up to 2 IVs.
3 IVs are chosen randomly amongst your parents, and then given to the offspring. Other 3 are random. Use this to your advantage.
It will take you a while to get the genetic monstrosity that you want. Plan ahead.
Any questions?