They say 90 percent of success is showing up. For frustrated consumers, 90 percent of success is speaking up. And yet, only 4 percent of unhappy customers ever bother to complain, according to 1st Financial, a customer-service training firm.

People gripe to their friends or whine to their spouses but don’t actually approach the company that did them wrong to make their grievance known. “Companies know that most consumers will not take the time to complain,” said Amy Schmitz, a University of Missouri law professor who has spent much of her career studying consumer dispute resolution. Schmitz wrote a paper explaining how some companies deliberately make it such a pain for consumers to seek resolutions to their problems that most give up and go away. “Some companies . . . reserve remedies for only those that remain persistent,” Schmitz explained. “It is true that squeaky wheels get the grease.”

So be the squeaky wheel — but make it a pleasant squeak. According to Schmitz, the “rule of three” for consumer complaints is to be polite, prepared and persistent. “Customer service representatives and managers are more likely to take you seriously and offer a remedy if you provide proof, succinctly ask for what you want and sound like a reasonable person,” Schmitz said.

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She’s right. Being polite is far more effective than cursing or threatening, which only will get you labeled as a crank. Being prepared sounds like a no-brainer, but many people don’t take the time to gather their documentation. As for persistence, decide up front whether the wrong you have suffered is worth it, and if it is, then see your complaint through to the end. Here are the steps to success.

Start at the bottom

People love to bluster that they took their grievance “straight to the top,” but usually that’s the wrong move. If you contact company executives first, they will simply send you to the front-line customer service folks. Show that you have gone through the company’s grievance process before you contact the bigwigs.

Make a specific request

Don’t demand “compensation.” Be specific about what will satisfy you. Years ago, my parents paid for the entire family to go to Hawaii. The door to the airplane wouldn’t close, we were delayed eight hours, we missed our connection and paid for condos we didn’t get to sleep in the first night. The airline gave each of us a $100 voucher for future travel but most of us couldn’t afford the rest of the cost of a ticket. So I asked the airline to instead give my parents two free tickets to return to Hawaii another time. I made my argument, made a specific request — and got a yes.

Be reasonable

Your specific request should be in line with your grievance. The “punishment” should fit the “crime.” If the tree company drops a limb on a section of your fence, you get a new section, not a new fence.

Social media

One study showed that 46 percent of consumers have complained to a company via social media — far more than complain through other channels. But another survey showed some large companies now ignore complaints sent via social media. I tried tweeting a company CEO to get some help but he didn’t actively monitor his feed, so I never got through to him that way. Sure, if you’re stuck on a plane on the tarmac, it’s worth a try. But if you have a more complex consumer grievance, check the company’s social media feeds first to see if it actively engages with consumers there. Then, when you post, ask the company for help rather than calling the company out.

Online dispute-resolution systems

Instead of engaging via social media, some companies are shunting customers over to other online or mobile systems where they can deal with the matter privately with a few clicks. For example, eBay has a resolution center and Uber has a customer help section in its app. This is not necessarily a bad thing. “Many of my students are amazed with how easy it can be to complain if you just take the initiative to give these ODR systems a try,” Schmitz said.

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Apps that complain for you

Keep an eye on the app stores because developers are starting to come up with software that does the dirty work for you. Case in point: an app called Service that tracks flight delays and disruptions and automatically seeks compensation for you.

Bypass phone trees

If you want to be old-school and call a company for help, waiting around on hold is ­everybody’s worst worry. Enter ­DialAHuman.com, a website that gives you instructions for bypassing the phone trees of hundreds of companies.

Consumer scores

You may think you are expressing your opinion of a company when you complain, but did you know the company may also have an opinion of you? “There are data brokers . . . creating ‘secret’ consumer scores that rank you on how likely you are to make certain purchases,” Schmitz said. “If your consumer score indicates that you are less likely to make large purchases with a certain retailer, then you may not receive the same perks or remedies as a customer they deem more ‘valuable.’ ” The solution? If you really are a loyal customer who is likely to make substantial or frequent purchases, be sure to tell the company that.

Email executives

If you’ve gone through the company’s dispute process and are still unsatisfied, it’s time to directly contact executives. You can find their names on their own website, LinkedIn or the Better Business Bureau, which lists contact people for most businesses. If you don’t see email addresses on those sites, create a free account on Hunter . Type in the company’s URL and it will generate the company’s email format or ­individual email addresses.

Snail mail

These days, sending an old-fashioned paper letter is a clever way to distinguish yourself. The resources above will help you find a street address. Whether you send your message via email or snail mail, triple-check it for spelling and grammar. Schmitz says some companies have artificial intelligence in place that flags errors and that could ­further degrade your “consumer score.” Include copies of your documentation — never originals.

Free help

Finally, be aware of the local, state and federal agencies that can help you resolve consumer disputes. For example, if you have a dispute with an insurance ­company, you can turn to your state insurance commissioner. USA.gov maintains a helpful page full of links to government agencies that regulate companies and help consumers. Start by CC’ing these agencies on the correspondence you send to the company. If that doesn’t work, you can file complaints directly with these government agencies. Just remember to be polite, prepared and persistent.

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