You shouldn't have a lot of your information on the internet because anybody can look at it and most likely can find you and hurt you or something like that. Always keep your settings private, so bad people don't look at your stuff.
Don't add people you don't know. Because if you don't know them they can look at your stuff and do whatever to it. Don't talk to people you don't know either, The reason for that is because who you might think that person is could be another person.