One of the most important word of mouth marketing tools is the idea of giving people something to share. Never let someone leave without something to give a friend. Offline, we're talking about handouts, samples, flyers, menus. Online, we're talking about downloads, emails, white papers.
Your goal: Every person who talks to you tells the next person they see, "I was just shopping at ___ and they gave me this." That object is a trigger that kicks off a conversation that wouldn't otherwise happen.
A simple example is this single sheet of notepaper at each seat in the meeting rooms at the Holiday Inn Dayton. Definitely nothing fancy — but you're more likely to keep it than that stubby notepad you usually get. And on the back… a tasteful promotion for the hotel.
Here's a cool-but-silly example created by Rafael Martinez Gallardo, one of my students at Northwestern, to promote our class blog: