I haven't entertained in a while, but I usually have two ways, one is to announce in advance what is on the menu (thereby they can determine they want to eat it or not or tell me they have problems with it), and the other is potluck.

I've been to a party once where the menu was bouillabase (sp?). It was awaful because I hate shellfish and anything fishy, so I tried to eat a bit but it just wasn't going down all that well. The host felt horribly as well because she thought she was putting on a fantastic meal and I couldn't enjoy it.