Mac computers are great devices: they’re fast, reliable and safe to use. But over time and with lots of use, even Macs start to slow down. Usually, it's a case of installing too many applications - particularly if these applications have the convenient option of automatically starting when OS X boots. While convenient sometimes, it can often lengthen your boot time, especially on non-SSD devices.
Here’s how you can stop any application from starting with the OS X to improve your Mac's performance and boot times:
Open up "System Preferences". Click on the "Users & Groups" icon. Then look for your user account on the left. Once there, click on "Login Items".
The screen below should pop up, showing which applications are opening automatically when you log in. To remove an application from this list, select it click on the button with the minus icon. You can also add an application to get it to start up automatically with a boot: either click on the plus button and browse to it manually or drag the application icon to the list.
You might be surprised what applications are opening automatically. You probably don't even use them! By disabling their automatic start-up, you can dramatically speed up your boot times.