John Osborn, chief executive of OMD U.S., is here at the Cannes Lions International Festival of Creativity "for one reason, and that's that our clients are here," he says.

"There is no shortage of meetings, but we’re trying to take a very intentional approach," Osborn says, explaining that OMD's focus "is more about driving revenue than drinking rosé."

Sure, "it's always been a place for folks to let their hair down," Osborn notes, but he advises advertising and marketing professionals on the ground to not miss the "raw, interesting conversations happening on the sidelines of the event." That's how attendees will get their return on investment, in his view.

"There's a lot here," Osborn says. "The sheer size and scale of [this year's event], I’ve never seen anything quite like it."

Outside of Cannes, speaking in general on proving ROI for clients, Osborn says everything about the media agency's role "begins and ends with the consumer."

"The consumer is in charge," he says. "You talk about ROI, return on investment, yeah, but it’s also return on interest. Fighting for that [consumer] interest and earning that interest is super, super important."

Amid all the chaos the parties and presentations along the French Riviera, which are certainly relevant to all the brands and agencies constantly fighting for attendees' time and interest at Cannes.