To give yourself some protection if you join Facebook, use a Nickname and some esoteric email address you never use, for example; join Facebook as Jean Picard with an email email@example.com.
If you already belong to Facebook as yourself, change the email. All the crap that now jams your email account ends. Don’t be open on Facebook.
Don’t say what school your kids attend, what city you live in, where you work.
Even if someone pops up claiming to be an old school friend, even giving details, they could be a scammer who has done a search of you.
Trust nothing on Facebook.
Facebook exists to make money for the owner. By any and all means.