Notifications are part and parcel of computing life on the OS X. Starting with OS X Mavericks, notifications even appear on the lock screen of your Mac. This is unfortunately the default behaviour. Notifications can be rather personal especially for those coming from Calendar, Reminders and FaceTime, and are not something you want on your lock screen especially for a Mac in public, office or school.
To disable notifications from appearing on the lock screen, go to System Preferences > Notifications. Select an app and uncheck “Show notifications on lock screen”.
You will need to manually uncheck this box for every OS X app that sends out notifications. Yes you read it right. There is no global switch to turn it off for all apps at once. Lets hope Apple build a global toggle for next version of OS X.