While it's true that most marketing companies won't have direct experience in a particular service, industry or field the theory of marketing remains the same. It's actually ridiculously simplistic when you really break it down, but it's the gathering of information and knowing what to do with that distinguishes the best marketers from the pack.
Marketing should always be focused on a target group of consumers since there is no product or service that can be attractive to all people. Defining the target market in the mainstream is usually done by using some demographic criteria (geographic, age, gender, class, etc.). However, there is a different way to differentiate and target consumers; focusing on values and beliefs they represent. That is the best first step in the marketing plan.
If a random group of people were asked how important to them is Product X or Service Y the majority would say that they don’t care. But there would be a minority (the qualified guess is 10% to 30% of the total market) for whom importance of these principles may be ranging from important to very important and even to crucial.
To build an effective marketing plan one needs to find out how the particular product or service varies in importance for the market within one's geographic reach and build the marketing program around the benefits that are most valued.
Effective marketing is about telling people what they want to hear.  Marketing is often confused with education, which is about telling people what they need to learn. A proper balance between the two, with emphasis on marketing, must be struck. Instead, it is very common for many businesses to focus on education. Extended information needs to be available and presented but only if customers want to learn. Their attention is gained and money follows if the message about the product is what they want to hear. And what they want to hear is something that should be figured out first by any marketer.
Marketing is all about telling a story. Besides marketing materials and media coverage, the story is being "told" through direct contacts, personality and appearance of people involved, attractive and informative websites, appearance of products, and promoting places where the food is produced (farm, shop or market stand), etc. All of these should tell the same, truthful story that targeted consumers want to hear.
Trust is not a simple thing.  It has two sides. It is about both integrity and competence of the person or organization. There are many big businesses that may demonstrate high level of competence but their integrity can be questioned and they are not trusted. The opposite can be equally detrimental, when businesses/people can be generally truthful but their competence may be questionable. For consumers that may be highly detrimental, undermine the trust and may heavily affect their purchasing decisions.
It is true that all marketers are story tellers, but not all stories are true. There may be strong temptation (learned from the mainstream) that the story, to be effective, has to be somehow embellished. Phrases such as the “morning mists”, “one big happy family” and “most delicious sausage you ever tasted” can undermine credibility of the offer. Caution is needed when telling a story - it needs to be connected to reality. What is needed is the understanding of what the targeted consumers want to hear and then matching it with what the business can actually offer.
Being truthful is fundamental to marketing, but trust is something that is often built over years and can be lost in a moment. It will inevitably happen if there are attempts to manipulate the message and not deliver what is promised. Sooner or later faking the message comes to the surface. The sellers may not even have idea how many customers have been lost or never gained because of their manipulation of the message. But the trust can also be lost if the products or service  don't match expectations and the story told about them. Integrity and good intentions don't suffice here; there must be business competence demonstrated as well or at least that need to match the marketing message forwarded to consumers so they know what to expect and accept some possible shortcomings.