There are two types of startups - ones that grow primarily through word of mouth at first, and dead ones.
During the early stages, customer acquisition through traditional means (ads, content marketing, etc) are too expensive and time-consuming. Your growth depends on a product so startlingly useful customers can’t help but share it.
So, let's figure that out.
The Growth EquationMost people think an objectively "great" product drives word of mouth, but it’s usually the least important variable in the growth equation. And, most importantly, it can't exist without the other two:
The Promise is straightforward but diabolical. A great business is just a promise your customer desperately wants you to keep, and the key to a good promise for startups is to have it drive most people away. This is due to the cost of a “bad” customer - they’ll take up your time and resources, give unreliable feedback (since they weren’t the target), and won’t recommend the business since it won’t be startlingly useful. If you have a bad promise, you might not know you've got a bad customer, and you'll be in for a world of pain.
So, your goal is to only work with early customers that you're sure will get enormous value from your first product, because you need to all but guarantee they’ll recommend it.
This comes down to the clarity of your promise.
If you’re helping restaurants with their finances, you want to help the restaurants that are most disproportionately impacted by the thing you’ve built your unique expertise around. A customer who's scarcity and constraints line up exactly with what you’re uniquely good at.
You don’t want to make a promise like “your restaurant’s finances are a mess - we’ll help you clean ‘em up so you can get profitable and grow,” because then you’ll get a bunch of different types of customers at different parts of their journey. There’s no way you can build something startlingly useful for all of them.