Check for software updates.
Often, software updates fix bugs and glitches that could be slowing your computer down. Check for any software updates that may be available for the version of OS X your computer is running on. You can do this by clicking the Apple icon in the upper left hand side and selecting Software Update from the dropdown menu. In most cases, your Mac will probably issue a desktop notification to alert you when an update is available.
Try restarting your computer.
It sounds obvious, but sometimes your laptop or desktop just needs a good restart to get back up to speed. Try restarting your computer before jumping ahead to other options.
Close unused tabs in your web browser.
Open tabs in web browsers do take up memory, even if it is a small amount. This can build up if you're the type of person that opens, say, 15 tabs on a daily basis and never closes them. Try to get into the habit of closing out tabs once you're finished using them.
The same goes for apps, too.
Apps, like tabs in web browsers, can also eat away at your memory if you have a ton of programs open. Apple has a couple of handy keyboard shortcuts that make it easy to exit apps quickly. For example, holding Command, Control, and the media eject button will quit all apps and restart the computer after asking you to save your changes.
Reduce the number of apps that launch when you boot up.
If you have a bunch of different programs set to launch when you turn on your computer, it's going to take a while for your Mac to boot up. You can see exactly which apps are programmed to launch on start by clicking the Apple icon and navigating to System Preferences > Users & Groups > Login items. In this list, you'll see all the items that start up with your computer. Check the boxes next to each app and click the minus button at the bottom of the window to remove them.
Organize your desktop.
For some, this is a daunting task, but you may be surprised to learn that it can actually give your Mac a little performance boost. OS X treats each desktop item like a small window with its own memory footprint, according to Digital Trends. So, try reducing the number of icons on your desktop by combining similar items into folders and deleting items you don't use.
Use the Activity Monitor to see what's running in the background.
The Activity Monitor on your Mac does exactly as its name implies, which means it can alert you to sneaky programs that may be running in the background. Try closing these background processes to speed up your Mac by either opening the Utilities icon in your Apps folder or by simply typing Activity Monitor in Spotlight search. From here, you can see how many programs are taking up memory on your computer and end those processes.
Clean out your hard drive.
Over time, your hard drive is bound to get cluttered. Deleting old movies, photos, podcasts, music, and any other type of file you no longer need is one of the best ways to free up some disk space — which can ultimately speed up your Mac.
Delete apps you don't use.
Again — apps can chip away at your system's memory. If you downloaded a game, app, or program that you no longer use, get rid of it to free up some space.
Clear your browser cache.
If you mostly notice sluggish performance while you're surfing the web, it could be your web browser that's the problem, not your computer. Try emptying the cache to speed up performance. The directions are slightly different for each browser, but in general you want to navigate to the Settings menu, and head over to the History option.
Check to see if Spotlight is re-indexing your computer.
Sometimes if you've just applied a software update, it can take a while for Spotlight to rebuild its index of all your files. This could be one reason why your Mac seems to be running slow. To check of its indexing, simply click the magnifying glass icon in the upper right corner of your desktop.
Close widgets on the dashboard you don't need.
Like apps and browser tabs, these widgets also take up a little bit of memory. Head over to the Dashboard by pressing Mission Control button in your dock and selecting the Dashboard. Close out the tools you don't need.
