My friend Julian Velard is a musician and a geek. But as hard as JV drives his MacBook Proand he does push it to its limits, using live audio plug-ins for his keyboards onstagewhen the computer acts up, Im the one he texts for support. (Fairs fair: If I cant remember how to play a minor major seventh, Julians the one I call. Were all experts in something.)

When Julian called late last week, his MacBook Pro wouldnt turn on; it would get stuck on the Gray Screen of Stomach Pain Inducement and never move forward. Over chat, phone, and then in person when he made the trek from Brooklyn to my New Jersey home, I walked JV through my steps for resuscitating a Mac that wont start up. Let me share them with you too, since you may not have my number.

Step 1: Run Disk Utility

If your Mac wont boot, there could be many issues at play. But the one I like to rule out right awayor repair, if possibleis any problem afflicting the hard drive. The easiest first step on that front is to run Disk Utility. On a Mac running Mountain Lion, you can run Disk Utility by booting into OS X Recovery Mode.

Make sure the Mac is off. (If its not responsive because its stuck on a gray, blue, or white screen, just hold down the Macs power button for several long seconds until it gives up and shuts off.) Hold down the Command and R keys, and power the Mac back up again.

Eventually, youll end up on a screen headlined OS X Utilities. (Once you see that screen, you can release the keys you were holding down.) Click on Disk Utility. Then, click on your Macs built-in hard drive in the left column of Disk Utility. (Usually, youll see two listings for your built-in drive: The first includes the drives size, like 500GB, in its name; and nested underneath it is your drives friendlier name. You want that second one.) On the lower right of the Disk Utility window, click Verify Disk, and then wait while Disk Utility does its thing.

In Julians case, Disk Utility said that it had found errors and we ought to repair them. We clicked Repair Disk, and Disk Utility eventually claimed it had repaired some problems. But Julians Mac was still misbehaving, so we moved on to step two.

Step 2: Safe Boot

Safe Boot limits what checks and functionality your Mac focuses on during startup, and performs certain diagnostics. Its rare, but sometimes you can get your unhappy Mac to start up successfully with a Safe Boot, and then restart it normally, and everything returns to hunky-doryness.

Shut the Mac down, and start it up while holding down Shift. Safe Boot can take a while if it does indeed work. To get some feedback about what's happening, you might choose to start up while holding down Shift, Command, and V: That enters both Safe Boot and something called Verbose Mode, which spits out some messages about what Safe Boot is actually trying to do as it goes.

Be patient during your Safe Boot. If the Mac does start up, restart it from the Apple menu once the desktop finishes loading completely. If the Mac starts up normally, go on with your day. Otherwise, keep working through this list. In JVs case, his Mac wouldnt restart normally following a successful Safe Boot. So, we moved on to the harder-core options.

Step 3: Fsck for fscks sake

This step is actually kind of funat least when its not your Mac thats under the weather. Its fun because it feels so geeky.

Shut the Mac off, and start it up again while holding Command and S. Youre launching Single User Mode. You can release the keys when the intimidating black screen with messages in white text appears.

Wait until the command-line prompt appears, when all the text is done scrolling past. Then, youll type fsck -fy and hit Return. And wait. Possibly for several long minutes.

Eventually, after five different checks that take varying amounts of time, you should get to one of two messages: The volume [your Macs name] appears to be OK or FILE SYSTEM WAS MODIFIED. If you encounter the first message, type reboot and press Return. If you see the latter message, though, youll want to run fsck -fy all over again. You can retype the command and hit Return, or press the Up arrow once and then press Return.

Ideally, youd eventually get to the &appears to be OK message, type reboot, and find that your Mac now starts up perfectly. Julians Mac had other ideas.

Step 4: Reinstall Mountain Lion

Remember OS X Recovery from Step 1? You can use it to reinstall Mountain Lion, too. Boot into Recovery mode, and then click to install Mountain Lion and follow the on-screen prompts.

We tried that on Julians Mac, and after the whole installation process was complete, JVs Mac did start working again. Briefly.

Then, all the same problems started recurring: crashes, kernel panics, and eventually a failure to start up successfully at all. Uh-oh.

A brief but hugely important pause

Long before this step, long before even Step 1 in fact, you should know the state of your backups. Julians state was that he didnt have enough backed up. Thats a lousy state to be in. Ive gone through my own backup plan elsewhere. Recently, we did a series of backup stories, including "Backup basics" and "How to set up Time Machine." This is the moment you'll wish you read those stories.

At this stage in JVs process, I was very concerned about his data.

During one of our successful bouts of getting the Mac working for a while, Julian signed up for the online backup service CrashPlan and copied over his most important files to a pair of external hard drives. But his failure to back up religiously made the trying Mac issues Julian faced not just a frustrating annoyance and time-suck, but terrifying, too. He could have lost hundreds of files representing thousands of hours of work.

Step 5: Reset the NVRAM, because, why not?

In the PowerPC days, we talked about resetting the PRAM. On modern Macs, the real term is resetting the NVRAM. The name refers to special memory sections on your Mac that store data that persists even when the Mac is shut off, like volume settings, screen resolution, and similar options.

Resetting that data isnt harmful, and quite frankly its also rarely genuinely useful. But man, at this point, it cant hurt.

You might need to grow an extra finger or two for this one, or have a friend help you out. Hold down all of these keys: Command, Option, P, and R, and turn on the Mac. Keeping holding the keys down until you hear the Mac restart again. Apple says to let it restart just the one time; I usually listen for a second reboot, and then release the keys.

In some cases, after performing this step, your Mac will restart normally. In other cases, if your luck is as bad as Julians was, you might instead see a progress bar on startup. If the progress bar fills up and then the Mac starts up, youre likely good to go. In JVs case, however, his Mac actually shut down at around the halfway point in the progress bar.

It was time for Step 6. Oh, Step 6.

Step 6: Make a Genius Bar appointment

Julian and I went to my local Apple Store with his Mac. We made one rookie mistake, which Ill get to in a moment.

We explained the problem in detail, and went over all the steps wed already tried. That was good. The Genius behind the bar agreed that it was probably a hard drive issue, and wanted to check to see whether the drive simply needed reformatting, or actually exhibited bad sectors indicating it needed to be replaced.

While we were there, Julian realized he hadnt backed up certain important files that had been on his Macs desktop. The Genius we worked with (Adam) could get Julians Mac to boot in Recovery mode, as we had, and we were able to copy the other files from it. But our mistake was that wed left Julians external drives back home. So JV had to plunk down extra cash to buy a thumb drive at the Apple Store, onto which we then copied those other files.

After consulting with a second Genius, Adam rendered his verdict: Because the drive wasnt reporting any bad sectors, reformatting it and starting over would likely cure what ailed Julians Mac.

We returned to my house, fired up OS X Recovery again, and launched Disk Utility once more, choosing to erase Julians Mac completely. Then we reinstalled Mountain Lion again.

The Mac started up beautifully. Julian returned home to New York.

Several hours later, as he restored his data from his backups, Julians Mac started behaving badly again. Eventually it crashed hard, and again refused to start up.

Double uh-oh.

Step 7: Go back to the Genius Bar again

Sometimes, even the best experts get it wrong. The new diagnosis for Julians Mac was that it was, in fact, a logic board failure, and not a fault with his drive at all. Apple took custody of JVs MacBook Pro, and in a few days (and for nearly $300), the store will swap out the laptops logic board.

So did we waste all our time with the earlier steps? Hardly.

First, we managed to get Julians Mac usable enough to back up crucial data. That was probably the most important step we took.

Second, all those steps ruled out numerous other issues; it was because of the freshly-wiped hard drive that the new Genius was able to conclude a logic board failure was to blame for JVs Macs problems.

Lessons learned

So while our steps didnt work this time around, thats only in the sense of actually solving the problem at hand. They did help to ensure the safety of Julians data, and at least led us to the eventual answer. (Possibly, anyway. It could be that the logic board diagnosis is off-base, too.)

But having these steps and awkward key combinations committed to memory, or saved to an iPad, or stuck on your refrigeratorthat can make coping with your next Mac disaster considerably less stressful. Presuming your backups are current, anyway.