There's the explosive word of mouth we all covet as marketers. “I'll launch my product this week and by next week the entire Internet will be abuzz about it.” It's a nice goal, but just like winning the lottery, it's not a real plan.
Unless there is a major trigger like a news event, word of mouth tends to spread gradually over time. A few people hear of something new and one or two people share it, and so forth. Or a product launches, but it takes time for consumers to be impressed enough to tell others.
Any Sernovitz gives a great example of slow word of mouth gone wrong. “By the time you hear about a great new show on network TV, you've usually missed the first few episodes. You may miss the key plot elements and never catch up, so you stop watching.”
Which is exactly why networks are now broadcasting recent episodes from their websites and also from sites like Hulu.com. Just because a customer doesn't catch on right away doesn't mean you should make her feel alienated.
If you run an online program or membership of any kind, let newcomers catch up by having a section just for them. Odds are you're already doing this in any email series you might have. New subscribers get to start at the beginning of the series, regardless of when they join your list.
If you're blogging, don't assume readers have been with you from the start. In fact, no matter what you're doing in your marketing, always bear in mind that there are newcomers who are seeing you and your product for the first time. Make them as happy as you made your veterans who joined you on your big launch 6 months ago, and word of mouth will continue to spread, even if it happens at a pace that's slower than the latest viral dance video craze.