If you're trying to sell yourself to a customer or an employer, or to millions of voters who can give or withhold the world's most powerful job, your instinct may be to talk about yourself, detailing all your strengths and accomplishments. But as last night's Democratic Presidential Debate proved, sometimes the most effective thing you can do is to praise or support someone else.

Three of the most powerful moments in the debate came about when candidates -- all of them competing hard for a nomination that is very much up for grabs -- did just that.

1. Joe Biden gets the audience to give Lt. Col. Vindman a Standing Ovation.

I'm pretty sure this has never happened before in a presidential debate. Former vice president Joe Biden was in the midst of answering a question about how to beat president Donald Trump in a general election when he asked the audience to stand up and clap, not for anything he himself had done or said, but for Lt. Col. Alexander Vindman.

Vindman, a decorated Iraq War veteran, was a National Security Council employee who testified against Trump during impeachment proceedings in Congress. Earlier on the day of the debate, Vindman was dismissed from his post and escorted out of the White House by security officers. That's what prompted Biden to reference him from the debate stage.

It worked -- most of the audience did indeed stand up and clap. A very effective moment, and one that reflected at least as well on Biden as it did on Vindman.

2. Pete Buttigieg defends Hunter Biden.

Much of the debate played out as a contest between the old and the new, or perhaps the old and the young. The youthful/new contender was, obviously, Pete Buttigieg. At 38, he was the youngest person on the stage; if he were just five years younger, he would actually be too young to run for president. Not only is he young, he's new to the Washington scene, having only held elected office as the former mayor of South Bend, Indiana. 

Buttigieg came out of the Iowa caucuses pretty much tied to win with Bernie Sanders, which made him a target of the candidates he'd bested. Minnesota senator Amy Klobuchar accused him of selling himself as a "cool newcomer," and noted that Trump was also a newcomer when he took office. Biden, who is 78 and spent the whole evening reminding the audience of his previous experience in the White House and the Senate, leveled this criticism at Buttigieg: "I do believe it's a risk, to be just straight up with you, for this party to nominate someone who's never held an office higher than a mayor of 100,000 people in Indiana."

But then a question came to Buttigieg about the risk of nominating someone who is under threat of investigation, as Joe Biden is. Following the impeachment proceedings, Republicans have begun an investigation into his son Hunter Biden, raising the possibility that Joe Biden might be next. (The impeachment, of course, centered around Trump's request that the Ukrainian government investigate the Bidens.) 

It was an invitation to strike back at his older, more experienced rival, but Buttigieg chose to defend them instead, and call for unity within the party.

It was a highly effective answer that was met with prolonged cheering. And a lesson for all of us: Showing kindness to someone who has just attacked you is one of the most powerful things you can do.

3. Amy Klobuchar pays tribute to FDR.

Admittedly, saying nice stuff about a hugely popular president who is long dead is an easy choice for any candidate and it's a fairly common debate tactic. That said, Klobuchar -- who had the best debate of her candidacy thus far -- used this approach to hit it out of the park on her last at-bat. The candidates were each asked to reply to a final question about child poverty, also an invitation to deliver any closing remarks. So after talking about child poverty, she launched into an emotional telling of a story about president Franklin D. Roosevelt's funeral train.

Without precisely comparing herself to Roosevelt, Klobuchar continued naturally on to talk about what she would do as president, ending in a rousing speech where she repeated the phrase "I know you and I will fight for you," (a rhetorical device called epistrophe, by the way). The audience whistled and gave her a very long ovation, and afterward, Rahm Emanual, Chief of Staff to president Barack Obama, commented that with this debate, Klobuchar had gone from sounding like a senator to sounding like a candidate. 

So there you have it. Next time you're trying to sell yourself and can't think of the best thing to say, consider praising someone else. You pretty much can't go wrong. And you might just make a long-lasting impression.