Falling at the last hurdle
Word of mouth marketing has long since been regarded as one the most effective forms of winning new business. Everyone wants a recommendation from a friend or a friend of a friend. In fact these days it goes further than that and recommendations from strangers via private Facebook groups or even websites like checkatrade are just as valid.
Where businesses often fall down is that they spend a long time in the cycle of: marketing themselves > winning business > doing a great job and completely forget about after sales service. This is arguably where great organisations are set apart from ok ones. Yes, it takes effort once you have already sold a product or service and been paid for it. However you really can't put a price on the value you receive as a result of just 'doing the right thing'. It's often exactly because you don't HAVE to do it that not only makes it so rare but also so appreciated.
It's the reason shops like John Lewis have such a good reputation. But it absolutely doesn't have to just apply to the big players and I personally have experienced brilliant service from very small local businesses. Surely it's an obvious way of differentiating? It's about putting the customer first. I'd go as far as to say you can only really tell how good a business is by their after sales service.
People don't bother remembering mediocre service but amazing service (and awful service for that matter) is firmly committed to memory. It seems obvious, you're doing everything in your power to ensure returning customers and giving someone a reason to rave about you. After all, remember, everyone likes a happy ending.