College commencement speech season may be the best time to learn how to communicate powerfully. This season is off to a good start with President Obama at Morehouse College, Arianna Huffington at Smith, Steven Colbert at the University of Virginia and Twitter CEO Dick Costolo at the University of Michigan. From their talks, we can derive a few takeaways:

There’s no excuse for not knowing your audience.
Arianna Huffington and Steven Colbert show that if you do a little to understand your audience, you can connect with them much more effectively. Arianna told Smith grads that she had stalked them online to learn what they were thinking, doing and blogging about. She picked up a few tidbits to make the students laugh, to praise their achievements and to inspire them to higher callings.

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And after making the UVa grads laugh, Colbert showed his serious side to inspire them.

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People don’t care how much you know unless they know how much you care.
President Obama has been criticized for coming across tired and unenthusiastic. Business execs with too much on their plates take the same rap. My advice: Get personal. At Morehouse, Obama talked about wishing that his father had been present in his childhood and how he feel motivated to be a better father and husband…and a better man. Be brave enough to let your caring show.

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Acknowledge your weakness. It makes others stronger.
Highly successful people often have trouble acknowledging shortcomings. Twitter CEO Dick Costolo played up his vulnerabilities and limitations to show the students at the University of Michigan that you don’t have to be the most dynamic guy to run one of the most dynamic businesses in the world. That’s something to Tweet about.

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And let’s not forget: Keep it simple.
No compilation of commencement greats would be complete without referencing Steve Jobs’ speech at Stanford in 2005. The late Apple founder shared three “stories from my life”—and if you’re not one of the 17 million people who have watched the speech on YouTube, you might want to do so before you try your next inspiring talk.

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Mary Civiello is an executive communications coach. She works with leaders at companies and not-for-profit organizations including Morgan Stanley , Merck , American Express , AIG and MetLife .