If you want to perform some troubleshooting or maintenance on your MAC you can boot your MAC into safe mode. Safe Booting Mac OS X disables many of the nonessential services and extensions that usually start up when a Mac is turned on. It is easy to start mac in safe mode.
Starting up in Safe Mode also does a directory check of the startup disk, disables non-system fonts, turns off hardware accelerated graphics, stops file sharing, and clears cache files that could be the root of your problems. To start up in safe mode,
Shut down the computer completely. Press the power button to turn the computer on and hold the Shift key immediately after the startup chime is heard. This must be done quickly.
Continue holding the Shift key until a gray progress indicator is displayed on the screen. After a couple minutes the system should bring you to a login screen that clearly states “Safe Boot”. Log in with your username and password.
If you are interested to watch the items are being loaded on start up, you can press and hold Shift + Command + V
While you’re in Safe Mode, you shouldn’t notice too much of visual difference from the way your Mac normally looks.