You can ask, "First time here?"
If it's an experience that's fairly common, human beings are very good at looking for clues about where to go for more information or to get started. That tall desk in the back of the drugstore probably has a pharmacist behind it...
Often, though, especially in international travel or new experiences or emotional events, we just don't know. So why not make it easy?
Be obvious about it. A sign that says First Time Here in three or four languages is a fine place to start. You can explain that while you serve minestrone, the locals come for the gumbo. Or that you should keep that little tag from the customs form cause you'll need it when you pick up your luggage.
Sure, not everyone is going to read that page on your menu or press that button on your voicemail, but your smartest and often loudest prospects will. And that's who you most want to persuade. (PS Richard has a plugin that does this for Wordpress users.)