Be the salt of the earth
The "I Have a Question" section from the April 1999 Ensign does a wonderful job of explaining what this teaching means.
To summarize, in the Law of Moses when sacrifices were offered, the animal flesh or fruit or smoke was not given to the Lord. Rather it was the smell or savour that was given and was pleasing to the Lord. To make the smell sweet, salt was sprinkled on the offering.
As the article points out, "It is clear that under the new covenant the followers of Christ, as “salt,” are responsible for extending gospel blessings to the whole earth. “When men are called unto mine everlasting gospel, and covenant with an everlasting covenant,” the Lord explains, “they are accounted as the salt of the earth and the savor of men” (D&C 101:39). It is our privilege and blessing to lovingly lead our brothers and sisters to Christ, helping them receive their covenant blessings. As we do so, we become the figurative salt that makes it possible for them to offer the acceptable sacrifice of a broken heart and a contrite spirit. In addition, our own covenant sacrifice of time, talents, and means is pleasing to the Lord."
Therefore, to be the salt of the earth means we are to love and lead and be missionaries in all that we do.
Just as a side thought … how interesting it is that the restored Church is headquartered in Salt Lake City Utah.
Be the light of this people
The second part of this lesson is that we should be the light to the people (be an example of righteousness). The point of this (in my understanding) is that we need to show our works and be in the world but not of it. We could not "salt" the earth if we lived in an isolated environment. We need to be "out and about" showing our light and not in some remote land where we could not influence those not of our faith.
Believe in Christ
Believe his teachings and follow them. The first principle of the Gospel is faith in Jesus Christ.
Repent of your sins
Repent of breaking commandments that Christ has given us. The commandments are found in this very chapter of 3 Nephi.
Have a broken heart and contrite spirit
Be humble and willing to submit to the teachings of Christ.
Do not be angry with your fellow man
Do not call him a fool (stupid, idiot) or any names. If you do, you will be in danger of hell's fire.
Lynn G. Robbins said the following, "A cunning part of his [Satan's] strategy is to dissociate anger from agency, making us believe that we are victims of an emotion that we cannot control. We hear, “I lost my temper.” Losing one’s temper is an interesting choice of words that has become a widely used idiom. To “lose something” implies “not meaning to,” “accidental,” “involuntary,” “not responsible”—careless perhaps but “not responsible.”
“He made me mad.” This is another phrase we hear, also implying lack of control or agency. This is a myth that must be debunked. No one makes us mad. Others don’t make us angry. There is no force involved. Becoming angry is a conscious choice, a decision; therefore, we can make the choice not to become angry. We choose!
To those who say, “But I can’t help myself,” author William Wilbanks responds: “Nonsense.”
“Aggression, … suppressing the anger, talking about it, screaming and yelling,” are all learned strategies in dealing with anger. “We choose the one that has proved effective for us in the past. Ever notice how seldom we lose control when frustrated by our boss, but how often we do when annoyed by friends or family?” (“The New Obscenity,” Reader’s Digest, Dec. 1988, 24; emphasis added). (Lynn G. Robbins, “Agency and Anger,” Ensign, May 1998, 80)
Before you come unto Christ, reconcile all your differences with your neighbors or acquaintances
Do not let disagreements last. The longer you wait to resolve differences, the harder it becomes to repent. Work out problems quickly before the problems grow too big to handle.
Do not look upon women (men) to lust after
It is natural to glance, but do not dwell on uninvited thoughts and be quick to turn away to resist further temptation.
Divorce is bad
Divorce is only good if it resolves a greater evil (unfaithful spouse, abuse).
Do not forswear (falsely swear)
You should be so honest in all that you say, that you should not even need to swear! When you say yes, it should mean yes. When you say no, it should be no.
If you are offended, do not seek revenge
First, let him treat you badly again and let the sting of his conscience rebuke him. If his conscience does sting him, he will repent and a friend will be gained. If his conscience does not sting him, leave him to God. Do not let anger and hate dwell in your heart. It may corrupt you more than the person that offended you. Leave it to God to handle. Always forgive.
Be kind to those who are in need
Lend to the borrower. Give to the beggar.
Do not hate your enemies, rather pray for them, and even serve them
If you can truly love your enemies, then you will have charity.
I will always remember the story President Hinckley related in his talk (Gordon B. Hinckley, “Forgiveness,” Ensign, Nov 2005, 81) about a woman who forgave a 19-year-old who threw a frozen turkey into the woman's car.
The news article from which President Hinckley read the account said, “How would you feel toward a teenager who decided to toss a 20-pound frozen turkey from a speeding car headlong into the windshield of the car you were driving? How would you feel after enduring six hours of surgery using metal plates and other hardware to piece your face together, and after learning you still face years of therapy before returning to normal—and that you ought to feel lucky you didn’t die or suffer permanent brain damage?
“And how would you feel after learning that your assailant and his buddies had the turkey in the first place because they had stolen a credit card and gone on a senseless shopping spree, just for kicks? …
“This is the kind of hideous crime that propels politicians to office on promises of getting tough on crime. It’s the kind of thing that prompts legislators to climb all over each other in a struggle to be the first to introduce a bill that would add enhanced penalties for the use of frozen fowl in the commission of a crime.
“The New York Times quoted the district attorney as saying this is the sort of crime for which victims feel no punishment is harsh enough. ‘Death doesn’t even satisfy them,’ he said.
“Which is what makes what really happened so unusual. The victim, Victoria Ruvolo, a 44-year-old former manager of a collections agency, was more interested in salvaging the life of her 19-year-old assailant, Ryan Cushing, than in exacting any sort of revenge. She pestered prosecutors for information about him, his life, how he was raised, etc. Then she insisted on offering him a plea deal. Cushing could serve six months in the county jail and be on probation for 5 years if he pleaded guilty to second-degree assault.
“Had he been convicted of first-degree assault—the charge most fitting for the crime—he could have served 25 years in prison, finally thrown back into society as a middle-aged man with no skills or prospects.
“But this is only half the story. The rest of it, what happened the day this all played out in court, is the truly remarkable part.
“According to an account in the New York Post, Cushing carefully and tentatively made his way to where Ruvolo sat in the courtroom and tearfully whispered an apology. ‘I’m so sorry for what I did to you.’
“Ruvolo then stood, and the victim and her assailant embraced, weeping. She stroked his head and patted his back as he sobbed, and witnesses, including a Times reporter, heard her say, ‘It’s OK. I just want you to make your life the best it can be.’ According to accounts, hardened prosecutors, and even reporters, were choking back tears” (“Forgiveness Has Power to Change Future,” Deseret Morning News, Aug. 21, 2005, p. AA3).
Ryan Cushing was sentenced to six months in jail, five years probation and five years psychiatric help and community service.
Be perfect like Christ who is like God