Steps to  fix troubleshoot common apple MacBook problems:

• difficulties with the start-up-If your Mac won't boot up properly and you're staring at a blank screen or a grey startup screen instead of your desktop, it's time to try Safe Mode.
• Login things that aren't compatible-When you turn on your Mac and see a blue screen, it's possible that one of your startup items is incompatible with MacOS. To do so, navigate to System Preferences > Users & Groups and select Current User on the left. Then, above the window to the right, click the Login Items tab.
• App isn't responding-When an app hangs, it locks you in and prevents you from doing anything, including exiting it. Enter the command: Force Quit. The Force Quit menu can be accessed via the Apple icon in the upper-left corner or by pressing Command-Option-Escape. Simply choose the non-responsive app and press the Force Quit button.
• Beach ball spinning-If you're starting to notice the spinning beach ball more frequently, it's time to investigate what's causing the lag. Open the Activity Monitor application.
• There is no access to the internet.-Click the Advanced button in the lower left corner of the Network tab in System Preferences to see a list of Preferred Networks. These are the Wi-Fi connections that your MacBook has remembered in the past for future usage.

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