I am quickly summarizing up the best way to speed up a slow mac performance:-

1. Find resource hungry processes

2. Close applications

3. Prune all the startup programs

4. Reduce transparency and animations

5. Use a light web-browser like Google Chrome

6. Disable FileVault disk encryption

7. Speedup the finder

8. Free up some extra drive space using software like Stellar Speedup Mac

9. Reset your SMC to fix all type of errors

10. Finally, reinstall Mac OS X

I am quickly summarizing up the best way to speed up a slow mac performance:-

1. Find resource hungry processes

2. Close applications

3. Prune all the startup programs

4. Reduce transparency and animations

5. Use a light web-browser like Google Chrome

6. Disable FileVault disk encryption

7. Speedup the finder

8. Free up some extra drive space using software like Stellar Speedup Mac

9. Reset your SMC to fix all type of errors

10. Uninstall Unused Fonts

Finally, reinstall Mac OS X if it is still slow.