“The Covid-19 vaccine demand heavily outweighs supply,” said a Rite Aid spokesman. “When the appointments are made available they are filled quickly.” An issue on the website, which didn’t hold your appointment slot when you’d start to input your personal information, has since been fixed, he added.

Congrats! You survived 12 months of pandemic! Now fragmented systems, shoddy websites and limited vaccine supply stand in the way of you and, well, the rest of your life.

It’s one of the most important human-vs.-machine battles of our time. And it’s made worse by the fact that most humans currently eligible to enter the fray are over 65 and not necessarily glued to a keyboard all day. Many sites don’t take appointments over the phone, either.

But let me tell you, these systems are maddeningly broken, no matter your age or technical skill level. From national pharmacy chains to hospitals to local supermarkets, every Covid-19 vaccine-appointment website I’ve been to has made me feel like I’m bad at computers. And I’ve, well, you know, been reviewing computers for nearly two decades!

So I set out to beat these Byzantine, Hunger-Game-like systems—and help eligible family and friends in the process, much like the generous, tech-savvy volunteers booking appointments for those in need across the country.

Along the way I met 34-year-old Kris Slevens, an IT guy who’s booked over 350 appointments for New Jersey seniors. He let me into his process, which includes setting up a browser tool and adding a couple of browser extensions. You don’t have to be some hacker or ticket scalper to master these tricks: In the subsequent week, I booked 11 appointments in five states, including Maryland, New York and New Jersey—some on the websites of pharmacy companies CVS, Rite Aid and Walgreens.

Does this mean you’ll be able to score an appointment as soon as you read this? I wish. This whole thing is like a Vegas poker game: You can increase your odds with some skill and good timing, but a lot of it is luck of the draw.

(What this guide isn’t for? Cutting the line. My advice will help book appointments for people whose states have deemed them eligible for Covid-19 vaccination.)

Step 1: Find local social-media groups and accounts

Because the U.S. lacks a centralized sign-up system, everything is localized to the state or county level. What works in one place might not work in another. So

Facebook

FB 1.15%

groups have popped up in most states, with members who scout the local websites and available appointments.

Many groups, such as the one that Kris moderates, help book appointments for in-need seniors. If you plan to ask for help from someone you don’t know, be careful. Don’t share highly personal information such as passwords or Social Security numbers. Having booked for many, I know that only basic contact info—name, date of birth, address, phone number and email address—is usually needed.

Head to Facebook and search for your state and “Covid vaccine.” In the New Jersey, New York and Maryland groups, I found active members providing minute-to-minute updates, links and even detailed spreadsheets about locations and appointments.

People have also created

Twitter

TWTR 3.31%

accounts to provide instant updates on appointment openings. To see how other states work, I offered to help a Maryland couple in their 70s. I followed MDVaxAlerts and set up push notifications on my iPhone. (Tap the little bell icon on the account page.) I was alerted to new openings at a CVS location and, within five minutes, successfully booked two appointments.

Some people have also built websites that aggregate all the locations in a state, such as this one in New York. Some other good resources for local information: Vaccine Finder, run by Boston Children’s Hospital; this AARP page, with information grouped by state; and this site that scans pharmacy sites for availability in different states.

Step 2: Learn the appointment websites

When you’ve picked a vaccine location, click to its website. Find the page that tells you whether appointments are available, and the page where you book an appointment. Yes, sometimes those are different. Once you have the links, bookmark them. I suggest using a laptop or desktop for all of this; working on a phone or tablet could slow you down.

If you’d like to get a vaccine through one of the big pharmacy chains, here are some specific tips:

• CVS: Start with the vaccine screening tool, a questionnaire about you and your eligibility. At the end, you land on a page where you input your ZIP Code and search for appointments. Keep clicking the ZIP Code to see whether new appointments have been added. If you get a slot, you’ll be asked to fill out a questionnaire longer than a mortgage application. Select “Don’t Know” if you’re moving fast and don’t have time to read each question. For the East Coast, it seems big chunks of new appointments appear around 6 a.m.

• Rite Aid: Start with the vaccine scheduler or this eligibility guide. After you’ve input your personal information in the scheduler, you’ll get a list of local stores that offer the vaccine. You actually need to select a location and press “Next” in the bottom right to see whether there’s availability. Go through the whole list of stores like this to see whether any have appointments. There are reports in many states of new appointments appearing around midnight Eastern Time. The Rite Aid spokesman said it’s best to check for new appointments frequently.

• Walgreens: Start with the vaccine-availability checker. Unlike the others, Walgreens requires that you have an account to book, so create one beforehand with all necessary information. Make sure you remain logged in on your browser. Walgreens also offers phone booking at 1-800-Walgreens. I have heard reports that new appointments appear at midnight. A Walgreens spokeswoman said timing varies based on inventory and appointment availability.

I didn’t use Walmart or any of the smaller pharmacy chains, but I suggest leaning on your local Facebook groups for information about timing and other site tips.

Step 3: Set up autofill

In your browser, locate your autofill settings. This will allow you to store your full name, email address, home address and phone number in the browser. When it comes time to fill in all this, the browser will drop it in—no time wasted typing or copying and pasting.

“Any way that you can get a millisecond faster than the other person is crucial,” Kris told me, “especially when you can have 50,000 people vying for one cancellation spot.”

In Chrome, go to Settings > Autofill. In Microsoft Edge, Settings > Personal Information, then click the edit button. In Safari, Preferences > AutoFill > AutoFill web forms > Using information from my contacts.

Step 4: Install browser extensions

Now the hard part: Staying up-to-date on these sites and available appointments. Appointments can disappear minutes after they’re released, so in addition to the Twitter and Facebook resources, I’ve used two tools to try to catch them.

The first is a browser extension called Page Refresh. It will refresh the page you’re on every few seconds or minutes, without you clicking anything. I keep this open on my second monitor. It’s available for Google Chrome and Microsoft Edge (and similar extensions are available for other browsers). The Page Refresh developer says the extension doesn’t collect any user data.

One important tip: If you see an open appointment, stop the refresher ASAP. If it refreshes while you’re inputting information, you could lose your place.

That solution requires you to keep your eyes on the page. A tool called Visualping can do the watching for you. You tell the service’s website or browser extension what website to monitor, then you highlight the part of the site that you expect to change—in this case something that reads “no appointments” or “appointments booked.” If it changes, you get a computer notification or an email alert.

For sites such as Walgreens and CVS that require your ZIP Code to check for open appointments, you can set that up with Visualping’s advanced tools as well.

The free version of Visualping lets you watch two websites, but it only scans once a day. That isn’t going to cut it. I tried the $58-a-month version, which scans every five minutes, and caught an email that led me to a successful booking on a hospital’s website. The free browser extension is more economical: It allows you to set the cadence to a minute but you’ll have to be at the computer to receive the notification—no email alerts. Visualping created this tutorial and list of Covid-19 vaccine sites to monitor.

Step 5: Book

And then…you wait. When that appointment pops up, breathe. It gets intense. According to my Apple Watch, my heart rate has risen five to 10 beats a minute when I’m booking.

Move as fast as you can but not so fast that you don’t read the messages and the prompts. None of the sites are as slick as Ticketmaster, with that helpful booking timer.

Generally, you can skip adding insurance info. If it’s needed, you can show it at the appointment. And if you have the option to choose from a variety of days and times, don’t choose the first slots. Go for something in the middle, where demand isn’t as intense. Most people try to book the first available appointment, Kris said.

Whatever happens, please just remember: It isn’t you; it’s the Covid-19 vaccine-booking website. You’re smart, you’re capable and you’re damn good at computers.

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Write to Joanna Stern at joanna.stern@wsj.com