It doesn't matter if a computer is brand new or several years past its prime, it seems like some relative you bump into over the holidays will always have encountered a problem with it. Macs are pretty easy to take care of, but you still have to deal with all of the common issues that hit any computer over time: slow downs, lost files, broken apps. Here's what you can do to get a troublesome Mac in good shape again without missing too much family time.
Update software (and maybe the OS)
The Mac App Store makes it really easy to keep apps up to date, but it's also really easy to keep clicking "ignore" when it prompts you to investigate and potentially install new updates. One of the simplest things you can do to make sure a Mac is functioning well is making sure its software is up to date. To do so, open up the App Store, click the update tab on the top right, and see what updates are available.
Installing security updates is a must
If there's a software update, there's little reason not to accept it. You'll also want to be sure to accept and install any security updates to OS X, which should appear near the top of the list. That's really your top priority here.
The harder question is whether you want to update someone else's Mac to a new version of OS X. New versions are generally a good thing: they have new features, they tend to move toward being easier to use, and apps are going to focus their new updates on supporting them. The downside is that operating system updates are sometimes known to slow a computer down over time. They might also rearrange buttons or rework functions that a person is used to using. And by the time they figure that out, you might not be around to help reorient them.
One possible rule of thumb? Don't update if you know it's going to make major changes to something a person uses day to day. Or, at the very least, ask permission and explain that there's no easy way of going back before doing so. My parents are still on Mavericks; I'm sure they'd manage just fine — hi Mom and Dad, I know you're reading this! — but I'm not convinced I should force Jony Ive's colorful redesign on them.
Stop unwanted apps from opening
Once you figure out which apps a person regularly uses (and which ones they don't), it's worth making sure that nothing unnecessary is opening every time they start their computer. To prevent apps from opening at startup, click on the Apple in the top left corner of the screen, select to System Preferences, and then choose Users & Groups. From there, you can select the Login Items tab at the top: that tab will show you a list of every app that opens at startup. You might think that checking or unchecking the box beside them would stop them from opening — but no, that just controls whether you see them or not. You have to click on the app you want to remove, and then click on the minus button below. Do that for anything and everything you don't need. Don't worry, you won't hurt much, even if you remove iTunesHelper. (One additional note: if you can't make changes, you'll need to click the padlock in the bottom left corner of the window and enter the account password; it should work after that.)
Remove what they don't need (and keep everything they do)
Your first instinct will be to drag every last icon out of a person's dock because, really, do they actually need quick access to Photo Booth and Keynote and Launchpad and Contacts and so on? Do not do this. Just, do not. Leave it. You wouldn't rearrange someone's living room; don't rearrange their dock either. It doesn’t matter that it looks just like the showroom.
Look at an overview of the drive to see how space is being used
What you can do is remove apps and files that person doesn't need, especially if their hard drive is starting to get full. A good place to start looking is the downloads folder, which is where a lot of files can start to pile up. But, once again, you're better off showing someone how to get rid of files on their own — deleting another person's apps and documents is a quick way to accidentally lose something important.
To see how a person is doing on storage space, click on the Apple in the top left corner of the screen and then choose About This Mac. In the center is a tab called Storage. Click on that for a breakdown of how all storage on a computer is being used. It can tell you whether storage is being dominated by photos, apps, music, movies, or other types of files. (If you want to get exceptionally detailed and nerdy about this, download the app GrandPerspective for even more detail.) The Storage tab won't tell you where those files are, but you can probably take a guess: music and movies in iTunes, apps in the Applications folder, documents in Documents, photos in Photos, and so on. If there's plenty of space free, then there's nothing to worry about. But a nearly-full drive is liable to slow things down, so it's worth clearing out anything that isn't in use.
Buy your way out of this problem
Okay, not every problem has an easy solution. But Black Friday is coming up, so you might just have a way out: buy a new Mac. If a Mac is really old and has been running slowly for a while now, that’s a good reason to consider getting a new one. In general, anything more than four or five years old is in the replacement range — it’s really a matter of how patient its owner is at dealing with its slowdowns. Plus, with Apple just adding a Retina display to its small iMac, now’s not a bad time to consider replacing a home’s desktop Mac.