You can speed up your Mac from 15 aspects:
1.Find resource-hungry processes
If you see that some app is using a lot of CPU power, you can close it from here by choosing the app and the mouse and clicking the X in the left-hand corner of the Activity Monitor.
2.Manage your startup items
A clean startup helps speed up slow Mac.
3.Turn off visual effects
Here’s how to speed up a Mac by turning off some visual effects:
(1) Click System Preferences > Dock.
(2) Untick the following boxes: Animate opening applications, Automatically hide and show the Dock.
(3) Click on Minimize windows using and change Genie effect to Scale effect.
4.Repair disk permissions
Follow these steps to repair disk permissions:
(1) Open Disk Utility (Applications > Utilities).
(2) Choose your startup disk.
(3) Click the First Aid tab.
(4) Click Repair Disk Permissions to repair any inconsistent permissions.
Note that beginning from OS X EI Capitan, there is no need to repair disk permissions.
If you recently updated your OS, you would be aware of the slowness that occurs when Spotlight is indexing. This only takes a few hours and then your Mac will be fine. But sometimes the indexing gets stuck, and you need to speed up a Mac To solve this problem, you need to reindex Spotlight by going to System Preferences > Spotlight and clicking on the "Privacy" tab.
6.Manage syncing photos to iCloud
Synchronizing photos to iCloud can take a lot of time and therefore slows down your Mac. So just shut down the iCloud Photo Library on your Mac.
7.Empty the caches
Over time, these cache files take much storage on your Mac.
So how to speed up MacBook by emptying the caches? There are two ways: you can clean them up manually (step-by-step) or you can remove them in a second with a cleaning utility iMyMac's Mac Cleaner.
8.Uninstall applications you don’t need any more
9.Clean up Mac’s hard drive
iMyMac's Mac Cleaner app has everything you need to finish the 3-hour task of hard drive cleanup in under 5 minutes. Even more, it will clean up the junk you didn’t even know about and speed up Mac.
10.Upgrading to the latest OS and upgrading your hardware will typically solve a bunch of slowness issues.
11.Restart your Mac
12.Reset SMC & PRAM
13.Replace your HDD with SSD
14.In fact, upgrading RAM is usually a great solution for improving your Mac’s performance.
15.If you don't feel like spending the next several hours trying to get your Mac in shape manually, there is a great solution. Download iMyMac's Mac Cleaner and let it do the job for you. It's a powerful utility for speeding up Mac It knows which files are useless, where they are, and how to remove them completely. iMyMac Mac Cleaner is incredibly easy to use: all the tools we've talked about, and even more, are right there, ready to launch in a Few clicks. No wasted time, just a faster Mac.