In case you didn't already know, your website is all about your customer, not about you. When a potential customer visits your site, they should immediately understand why they are there, and how they will benefit. You have their attention for about six seconds — to communicate your value — before they decide whether to stay or whether to leave.
Walk a mile in their shoes.
It's best to apply the WIFM principle (what's in it for me) when communicating with your customers. If you have a hard time putting yourself in their shoes, try facilitating a simple usability study to learn what they're expecting to gain from visiting. Put aside your ego and open your eyes & ears. You may be surprised at what you learn about their preferences.
The definition of success.
The customer benefit may not be monetary, or about what kind of deal they can get. Financial-related institutions often talk about "trust" or "quality of life" rather than money. Your audience will feel successful when they discover a connection between what they're looking for and what you're offering. A shared set of beliefs, values, and meaning is a strong foundation for any good relationship. Make a connection and win them over.
Clear as a bell.
Sometimes it takes a couple sentences or a whole paragraph, sometimes a single sentence or just a great a tagline, and sometimes it's only a word or two that rings true with your audience. But be sure to speak their language. If they aren't multi-generational, speak to them in a voice and tone that resonates specifically with their generation. Find the word(s) or phrase(s) that cut to the essence of the benefit your product or service is providing them.
When all is said and done.
Remember, you don't have your customer's attention and commitment until they're confident they're in the right place. If your tagline doesn't express the benefit clearly, be sure to express it near the top, above the fold or first screen load. Give them the reason(s) to invest their precious time on your site. Keep them on your site by making the benefit clear along every part of their journey.
Think of your website like an excellent wait staff — always one step ahead of you — attending to your desires so you don't have to do a lot of thinking. These principles apply to any site, whether it's for a simple small business or for a complex large enterprise. The clearer the benefit is, the better chance they'll want to engage.