If I were to rank the effectiveness of each marketing avenue for most businesses I've worked with, here's how they stack up.

1. Word of mouth
2. Email Marketing
3. Organic SEO
4. Paid Search
5. Display Advertising

In many ways, items 2-5 are easy. They have well-established best practices to follow. Word of mouth advertising, or viral marketing, is a different beast. How do you stimulate this activity among your customers? Is it possible to create this type of genuine buzz, or must it come organically? This question reminds me of the in-house debate among SEO's over the most effective link building strategy. Do you build, buy, or beg for links or do you create powerful, unique, and engaging content that transforms your site into a natural link magnet? If word of mouth was as simple as throwing up a YouTube video or creating a Tell-a-Friend page, everyone would drop traditional paid advertising methods such as search, email, or display ads. Obviously, a truly successful viral marketing campaign depends requires more.

Simpleology gives a brilliant break-down of the 2 main types of word of mouth marketing.

Incentivized Word of Mouth This type of WOM marketing attempts to stimulate viral marketing through incentives, usually monetization. An example would be a refer a friend program that allows customers to earn store credit by getting friends to buy.

Inspired Word of Mouth Inspired WOM marketing, in contrast, occurs naturally and without incentives. This can be as simple as one soccer mom telling another about the great experience she had at a hair salon, or an influential blogger who reviews a product he or she had a great a experience with. Customers who engage in inspired WOM marketing typically aren't just customers, they're raving fans. Their passion may be based on the product, service, or the entire experience. In all likelihood, the customers that are engaged in this type of WOM are your top 1,000 fans. So how does a company create genuinely inspired WOM? Back to the Basics In reality, I believe the most successful viral marketing comes as a result of only 2 things:

1. Creating products that are actually worth talking about and or...
2. Providing legendary customer service that consistently exceeds expectations

The simplicity of this formula is great news for many e-tailers, who will never be able to create a successful viral marketing campaign. For example, how does a website selling printer cartridges stir up viral buzz? Simple, they just do what they know best. They run their business with excellence and by providing an outstanding mix or products and service. Why do so many viral marketing campaigns fail? Because they're trying to create something from nothing. They're attempt to create buzz results in hyped up, blatant, and sometimes tacky advertising tactics. In contrast, consider Starbucks, who recently closed their doors for 3 hours in order to refocus on customer experience by learning to make better coffee. Like Starbucks, many online retailers need to get back to the basics, take a "coffee break", and refocus on what they do best. When this happens, inspired word of mouth will follow.