Deval Patrick, resplendent in a red-and-black robe, looked through a cold drizzle and told a big fat fib.

Maybe that’s a bit harsh. OK. He misspoke. But as he stood on the stage in McGuirk Alumni Stadium at the University of Massachusetts Amherst he certainly veered from the truth.

Because during his 2014 commencement speech, he assured me and 14,000 others that he realized how eager we were to get to our graduates, to take their pictures, to savor their achievement, to buy our families nice celebratory dinners.

I’ll be brief, the Commonwealth’s chief executive promised us — words that were greeted with a palpable sense of relief and head-nodding gratitude. I remember smiling at that moment.

And then he went on for hours — at least it seemed like hours — in a coma-inducing speech about how really, really important it is that we get rid of fossil fuels. Yes, he talked about petroleum policy with the zeal of someone auditioning to be US secretary of energy.

The response? Graduates puffed on cigars. Beach balls were swatted from the Landscape Architecture Department to those smarty-pants in the section reserved for the Isenberg School of Management. Some students blew bubbles.

I sat there and steamed. My mind wandered. Questions arose: We’re not going to make those dinner reservations, are we? What’s the matter with the Red Sox bullpen? Mike Dukakis was way more charismatic than this guy, wasn’t he?

You know you’re in trouble when the best line in your address, the line that brings cheers from the graduates and smiles to the faces of their guests, is this: “And in conclusion.’’

I offer this today as a cautionary tale. America’s college capital is primping itself for 2016’s commencement ceremonies. Graduation speakers have been selected and they are, doubtlessly, hard at work polishing their prose.

So I spoke this week to one of the foremost speechwriters of our time and asked him if he embraces the golden rules of public speaking: Be sincere. Be funny. And be seated.

“I think that’s good advice,’’ Jon Favreau, the North Reading native who served as President Obama’s chief speechwriter, told me on the phone from California.

My belief? Anything past 11 minutes is wasted breath.

“Man, I’m with you,’’ said Favreau. “I think 10 minutes is the ideal. Fifteen minutes is OK.’’ Beyond that? Cue the beach balls.

Favreau, who once wrote speeches for 2004 presidential candidate John F. Kerry, left his White House job in 2013. Along the way, he penned some of Obama’s most memorable speeches, including his first address to a joint session of Congress. He rose to become the second youngest head speechwriter in presidential history.

His advice? Respect the audience. Recognize that they care more about celebrating educational achievement than listening to some duller-than-dirt policy address.

“President Obama and I would talk about this every single year we did a commencement together,’’ Favreau said. “There’s certainly a few where he’s covered issues and policy but, by and large, he’s recognized that the commencement is not really a place to talk about issues or politics.’’

Favreau, a 2003 graduate of the College of the Holy Cross in Worcester, gave the 2014 commencement speech there. “It’s an incredibly difficult assignment,’’ he said. “It’s also an incredible opportunity.’’

Another tip: Introduce humor, but in a way that does not seem forced or fake. “In this day and age, when attention spans are so short, people can only absorb one or two or at the maximum three lessons,’’ Favreau said. “The speech should tell a story and not just in the anecdotes that you use, but you should tell an overall story about one thing.’’

Above all, think brevity.

“The president always used to tell me when we were working on speeches – he’s a writer and he would write long and I would write long – but by the end he would always say, ‘You know, I gave a speech in Boston once that was only 18 minutes,’ ’’ Favreau told me. “He was referring to the 2004 convention [keynote] speech. So that was a rule of thumb we’ve always tried to follow.’’ What a wonderful rule.

A few years ago, I was at a commencement address in Worcester. The speaker walked up to the lectern and pulled out one of those old-fashioned alarm clocks, one with two small bells on the top. He promised to be through before those bells tolled – in 10 blessedly short minutes.

I swear the guy hit his closing sentence just as bells rang. And the crowd went wild.

Thomas Farragher is a Globe columnist. He can be reached at thomas.farragher@globe.com.