Whatever you happen to find most suspcious.  Christopher28 is going for the lower decks, but you could still look for a more specific ship section to examine, or try and figure out which of the parties has the High Priest in it so that the reception can be planned better.  The way Krozer is running things, he's going to put a party of 40 people in your reception hall, too many to easily fight off without losses if it comes to voilence.  (unless you guys have rigged the place with explosives underneath anything that can be used for cover, which carries its own risks.  I think you'd have to buy a poison gas trap seperately, if you wanted to go that route)