How should marketers deal with Word of Mouth marketing?

Because it's a better way to market the product/service, And it's unpaid form in which satisfied customers tell other people how much they like a business, product, service, or event.
It's one of the most credible forms of advertising because people who don't stand to gain personally by promoting something put their reputations on the line every time they make a recommendation.

the marketer should know that 1 word can let you gain 5 clients and another can let you lose all clients you got so its all about the reputation & recommendation

Teeth 

To put it most simply, word of mouth marketers and advertisers seek to create something worth talking about and then actively encourage people to talk about it. As I referenced earlier, people love referrals. They tend to trust the opinions of their friends when making purchasing decisions.

marketers should feed it.

feed it as in give it full attention

 

it is the only free marketing incentive we have.

Unless marketers have a well laid out strategy that weeds out incentivised WOM props, I suppose the only way out is to create 'more than' WOMs.
Another way would be to keep informing customers through dedictaed channels to identify real from incentivised (as banks did over a period of time to teach customers not to fall prey to phising etc.
).
I read a hotel review on expedia and I don't know which is true.
There will be so many gimmics to try confuse customers.
I trust at some point marketers will reach a level wherein they can do only 'so much' of incentivised WOMs.

Marketers should definitely not provide an incentive to consumers and rely on the sincere recommendations as those are the ones that usually generate the most conversions of customers.
By providing excellent customer service and good quality products, there is no need to pay anyone to gain success, the product will speak for itself.

With the diffusion of computer and information technologies throughout businesses and homes, the field of marketing has made a significant transformation.
Worldwide, people have adopted the Internet as an communication, information, transaction, and distribution channel.
Marketers have to deal with consumers who increasingly interact with other consumers through the Internet.
The Internet dramatically facilitates consumer interconnections.
Email referrals, forums of users and newsgroups, as well as customer reviews encouraged by retail websites allow consumers to “spread the word” and share information far more easily than ever before.
Consumers find it important to hear the opinion of others while (or before) making purchase decisions.
They talk and discuss their purchase intentions with family members, relatives, friends, and on the Internet and ask for their advice.
As a result, receivers are most likely influenced in their decision-making because they interact and communicate with others.
There are a lot of factors that influence consumer decision-making and buying behavior.
With the rise of the Internet, many researchers have started to conduct studies to examine existing theories to the context of computer-mediated environments.
This thesis follows suit by researching the following problem statement: "To what extent influences electronic Word-of-Mouth, in the field of music, the receiver's purchase intentions?" Word-of-Mouth (WOM) is a concept with a long history.
Electronic WOM (eWOM) or word-of-mouse is basically the extension of traditional WOM on the Internet.
eWOM is found more trustworthy and credible than advertising and other marketer dominated sources.
Receivers and senders in the WOM process both gain from the exchange.
WOM gives receivers more information about choices they have, which may serve as valuable input in their decision process.
Thus, information and communication within online communities can trigger members to engage in consumption activities related to the community’s topic of interest, e.g., music and artist.
Information processing is related to both the ways in which consumers differentiate between alternatives and the effort they are prepared to invest in the decision task.
Communication effectiveness (like eWOM) can be overseen by increasing individuals’ levels of motivation, opportunity and ability.
In this research six variables have been researched which have influence on the influence of eWOM on the receiver's purchase intentions; Electronic Word-of-Mouth, receiver's purchase intentions, motivation to process information, opportunity to process information, ability to process information and information sources.
I have gathered data through a online survey (141 respondents).
The most important findings of this thesis can be summarized as followed.
Opportunity and ability did not significantly impact eWOM, whereas motivation did have a significant effect.
The results provide evidence that the variable 'motivation' offers a valid approach to providing theoretical and managerial insight to the phenomenon of eWOM.
I have demonstrated that the Internet not only serves as an information source, but that it actually influences consumer decision-making.
It indicates that the amount of information available on the Internet has an influence on eWOM's influence on the receiver's purchase intentions.