I'm trying to ask myself the same question, and my current process is either wanting to play a top tier deck like Reshizard or Gardevoir / Sylveon, or maybe I'll have a rogue idea to come up with at the event. Either way, I'l just want to know what I'm doing with the deck and prepare for all possible match-ups in advance. I consider the following:
-Reshizard
-Gardevoir / Sylveon
-QuagNadel
-Blacephalon (the baby one from Unbroken Bonds)
-Zapdos / Jirachi / *insert Pokemon here*
-PikaRom
-Blissey
-Probably 7 more I missed.
I want to be prepared for all these match-ups one way or another, and whatever deck you choose to play for Intercontinentals I'll at least tell you having a good match-up spread helps a lot. For example, having a much easier out to Reshizard with LOT Slowking OHKOing Reshizards, or Fairy Charm Lightning for Gardevoir decks to take care of PikaRom mainly. I've learned though to not make your deck inconsistent by throwing in techs that make things a little clunky (for as much as I'd love to play SUM Araquanid to completley wall baby Blacephalon, the only other logical explanation I could say for running it is that it knocks out Jirachis. Actually, even then they're probably just going to run DGM Turtonator to get through that sooo....).