This is a tough one for me because I've tried several things in the last few years that DON'T work. I've used several different "message map" formats, and you can find a lot of examples online. The online formats are good, very professional, well-structured. They are useful ways to think about what you are saying & why you're saying it.
But I find that my audiences internally struggle to use them, no matter the exact format. Even reinforcing with video training, quizzes, prizes, etc., hardly moves the needle.
Moving into this year I'm trying 3 new tactics and we'll see if they get more consistent results:
1) Collateral
2) Storytelling
3) Selling paths
1) COLLATERAL. Rather than focus sellers on a formal template, I just tell them to speak from our publicly available materials. For reps, I am advising them to review our website and make sure they have their own way to talk through the message flow there. For our internal business development reps specifically, I'm advising them to refer to a specific piece of market collateral we made last year. This piece contains a complete high-level pitch for the product: leadership proof points, basic message, 6 differentiating features, 3 brief customer stories. So I tell the BDRs to use it as their "cheat sheet". This seems to have worked so far.
2) STORYTELLING. I buy into the idea that people remember a story better than a series of bullet points, and can relay it more convincingly. So I am turning customer stories (and a few made-up stories, think of the "in a world..." movie trailer format) into speeches that reps can give.
3) SELLING PATHS. I am laying out specific paths that tell our sellers a strictly defined way to sell a product through all the steps from engagement to close. Think of an "if they are X persona, say Y; if they ask about A, say B" format. The challenge is not boiling the ocean but so far we're on a reasonable path. I'll report back in 6 months how effective this has been! And if I can I'll share a template.