To reset a login password in OS X Mountain Lion or later, restart the Mac and hold down Command-R to boot into the Recovery HD partition. From the Utilities menu, choose Terminal to open it. In Terminal type:

resetpassword

and press Return.

In macOS Sierra and macOS High Sierra, an Reset Password assistant will launch. Choose the user account or admin account you want to reset the password for. Enter a new password, confirm the new password, set (if you like) a password hint and then click on "Next" to set the new password for the account in question. Choose to "Restart" the Mac and when the Mac boots up, use the newly reset password to login to the computer.

In OS X Mountain Lion, OS X Mavericks, OS X Yosemite and OS X El Capitan, a Reset Password window will appear that will list all the bootable volumes attached to your Mac. Select the volume that contains the account you want to reset and choose the user name that needs its password reset. Enter and verify a new passwords in the appropriate fields and, if you like, enter a password hint. Click Save and the new password is applied to the account.

In general, applications in macOS are packaged into a ".app" bundle that appears to be a single file but is actually a self-contained folder. Unlike Windows, in which an application usually installs a folder that contains the executable and supporting files, most of what an macOS app needs to run is stored within the .app bundle. Deleting an application bundle will remove that application's binary and all the supporting files contained within. Many apps, however, also install additional files in the user's Library folder, such as application preferences and caches.

To manually remove an macOS app, make sure the app is closed and head to the user's Library folder (in OS X Lion and above, hold down the Option key while selecting the Go menu from the Finder's menu bar and select Library). Here, you'll want to check for references to the application in the Application Support, Caches, LaunchAgents, and Preferences folders. Remove any files or folders that you are certain belong to the application you're trying to uninstall. You may also want to check the main Library folder by navigating to the top level of your hard drive and opening the /Library folder, although most applications will confine their files to the user-specific Library. Due to sandboxing requirements imposed by Apple, apps obtained from the Mac App Store are even easier to remove. Simply delete two items: the application file itself from the Applications folder and the application-specific folder in ~/Library/Containers (user's Library folder).

Another way to remove macOS apps is to use third-party tools. Take note, however, that automated tools can sometimes miss certain files or folders, and users employing these tools should always perform a manual check to ensure that all remnants of the application have indeed been removed. Finally, some applications (such as Cocktail) have their own uninstaller. Wherever possible, use the application-specific uninstaller for these applications.

Regardless of which method you choose, remember that leaving behind the occasional abandoned preference file is not likely to cause harm or performance issues. In general, removing the app bundle from the Applications folder and a file or two from the user's Library folder is enough to remove the application from the drive and free up disk space.

Battery Calibration

A Mac portable is just that: a portable computer. It was designed to be plugged and unplugged to allow the battery to discharge and recharge on a normal cycle. As such, if you use your machine plugged in all the time, then it is important that you discharge (or calibrate) your battery every so often. If you rarely use the battery, then Apple recommends completely discharging the battery and charging it again at least once a month. If you use your notebook frequently on the battery and plug it in to "top off" the battery, then a full discharge cycle is required less often.

Follow these steps to calibrate the battery:

1. Plug in the power adapter and fully charge your MacBooks's battery until the light ring or LED on the power adapter plug changes to green and the onscreen meter in the menu bar indicates that the battery is fully charged.

2. Allow the battery to rest in the fully charged state for at least two hours. You may use your computer during this time as long as the adapter is plugged in.

3. Disconnect the power adapter while the computer still on and start running the computer off battery power. You may use your computer during this time. When your battery gets low, the low battery warning dialog appears on the screen.

4. At this point, save your work. Continue to use your computer; when the battery gets very low, the computer will automatically go to sleep.

5. Turn off the computer or allow it to sleep for five hours or more.

6. Connect the power adapter and leave it connected until the battery is fully charged again.

Checking Battery Condition

If you hold down the Option (alt) key on your keyboard while clicking the menu bar battery icon, then you'll see a Condition option. The battery condition can be in either one of four states: Normal, Replace Soon, Replace Now, or Service Battery.

Normal means that the battery is operating properly. 

Replace Soon means that the battery is functioning normally, but is currently holding less charge than it did when new, and may need replacing.

Replace Now means that the battery is functioning normally, but holds significantly less charge than the battery when new, and needs replacing before it could possibly do harm to your hardware.

Service Battery means that the battery isn't functioning properly or your computer has noticed a change in its behavior. You should take your battery and/or computer in for servicing if this problem continues after a few restarts.  

Long-term Storage

If you don't plan on using your Mac portable for more than a six-month time period, then you'll want to properly store your Mac's battery with a 50% charge. This will ensure that it won't fall into a deep-discharge state, or lose capacity and therefore have a shorter life.

Temperature is also a huge factor when storing your computer. You'll want to ensure your Mac and its battery are stored in an environment where the temperature is between 50ºF and 95ºF (10ºC and 35ºC). Anything more or less, and you could seriously damage your battery over a long period of time.

First, trace the entire flow of electricity to your Mac. Check your Mac's power cord to ensure it is firmly seated where it connects to the computer as well as where it plugs into the wall. If it goes through an outlet strip or a UPS, make sure that's also connected and turned on. Also check that any surge protectors are still working - a power surge might have knocked them off. You can confirm that an outlet is good by plugging in something else, such as a light. If the outlet and all cable connections check out, make sure the power cord has no crimps, breaks, or other damage.

Once you've established that your AC power path is good, it's time to look at your Mac itself. Unplug everything you can - not the power cord, your mouse and keyboard if they're wired, and your monitor if it's not built in - but disconnect everything else and try pressing the power button again. If your Mac turns on, you know that one of your peripherals was at fault.

If your Mac doesn't turn on, it's worth trying to reset your Mac's SMC (System Management Controller), a chip that manages a number of hardware functions - including the operation of the power button. Directions vary by Mac model; see Apple's instructions for details (http://support.apple.com/kb/ht3964).

If you have a Mac laptop, its battery should last through most power outages, so you may not notice that you have a power-related problem until the battery runs out, at which point your Mac might simply appear to be dead. So try all the above tips, but also check your power adapter. If you have an AC cable attached to the adapter (as opposed to a plug going directly into the wall), make sure that cable is securely connected. If you have access to another AC adapter, switch to it briefly - that will tell you whether the original adapter is bad or whether it's something in your Mac itself.

Still no luck? In that case, it's time for professional help. An Apple Store or authorized repair center should be able to diagnose and fix the problem.

If you hold down Shift and Option (Alt) before pressing the volume keys on your keyboard, you could adjust the volume in quarter-steps instead of whole ones. In addition to using this Shift and Option (Alt) combination to control the volume more finely, you can also use it when you adjust the brightness on your Mac. Press Shift and Option (Alt), then press one of the brightness keys on a Mac keyboard, and you'll notice that the brightness changes in quarter-steps. This is nice if you find your display is just a bit too bright or too dim.