Although learning preferences vary slightly from generation to generation, a safe bet is to work with an expert who is a master facilitator. Even the notions of keynotes are evolving into a more participatory exchange of ideas. I mean soliciting the input of your audience and use it to predicate the outcome of the presentation. Involvement also has a lot to do with the emotional journey that the presenter takes your audience on. Inevitably, a good presenter is a tour guide leading his audience into joy, laughter, anger, fear and tears only to take them back to a place where they feel good about themselves and are ready to return to their jobs with some tools and a renewed sense of optimism.
Some presenters sound like infomercials trying to sell additional services or products.
Be sure to let your speaker know what you expect in a presentation. If his products are beneficial to your audience, discuss pre-selling the products by incorporating them into the meeting's educational budget or offer the speaker a copy of the mailing list to use after the presentation. Also I see an alarming trend which I call PowerPoint Syndrome, where presenters fall into the trap of overproducing and smothering the audience in technology so that eventually, the primary message gets swallowed. It is not the message. You don't have to spend a fortune to create a memorable event.