Taglines are a significant opportunity to position a company—not only to help explain what the company does, but what makes it different. But don’t write your tagline until you’ve determined your Brand Promise. The tagline is a more polished, succinct and catchier version of the Brand Promise.

What is the one thing you can say about your brand that your competitors can’t say? Something that is both credibly true and valuable to your customer—something you can promise them. And most importantly, something you’ll want your customer to take away from every engagement with your brand. That’s your Brand Promise. In marketing-speak, it’s called the value proposition. In human-speak, it’s simply why it matters.

This past weekend I was browsing the web site for Lending Tree. Their tagline is, “When banks compete, you win”—nice and succinct, and clearly valuable. Their Brand Promise would be something like “Lending Tree is the largest resource for obtaining online bids from lenders.”

When it comes to crafting a tagline and a brand promise, branding guru, Marty Neumeier, says, “The key is to focus on a single proposition. If you find yourself using commas or ‘ands’ to write your tagline, you may need more focus. The rule? One proposition per brand.”