Ask people how they chose a plumber, a dentist, an accountant or a shop they trust, and the most common answer is not an advertisement but a person: someone they knew recommended it. A referral from a trusted friend, colleague or family member is the most persuasive form of marketing there is, because it arrives with credibility no advertisement can buy - the recommender has nothing to sell and is vouching from experience. It is also, in a direct sense, free: it costs the business nothing to produce and tends to bring customers who are already inclined to trust and to buy. For a small business especially, word of mouth is often the single most valuable channel it has.
The mistake most businesses make is to treat this priceless channel as something that simply happens on its own. They do good work, satisfy their customers, and then wait, assuming that happy customers will naturally tell others. Some do - but far fewer, and far less often, than would if they were asked. A satisfied customer is usually willing to recommend a business they were pleased with, but it does not occur to them to do so unprompted; they are busy, the moment passes, and the recommendation that would have come easily never gets made. The gap between customers who would refer and customers who actually do is mostly a gap of asking.
Closing that gap is largely a matter of asking well and at the right moment. The best time is when a customer has just had a good experience and their satisfaction is fresh - a completed job done well, a problem solved, a purchase they are pleased with. A simple, genuine request at that moment - letting them know you grow through recommendations and would be grateful if they mentioned you to anyone who might need what you do - turns latent goodwill into actual referrals. It works best when it is specific and easy: making it simple for them to pass your details on, or to introduce someone, removes the small friction that otherwise stops a willing customer from following through.
None of this replaces doing genuinely good work, which is the thing being recommended and without which no amount of asking helps; the point is that good work plus asking produces far more word of mouth than good work alone. Some businesses formalise this with referral schemes that thank or reward customers who bring others, which can work well, though for many the simple, sincere ask is enough. What matters is recognising that the most effective and cheapest marketing a business has usually needs a small, deliberate nudge to happen - and that the businesses quietly growing on recommendation are, more often than not, the ones that remembered to ask.