Set your own default Facebook privacy level to a high level you feel comfortable with. While this cannot protect you from either technical glitches, or from well-meaning friends and family inadvertently sharing your content with a wider audience, on a day-to-day basis it will certainly help minimise the risk of people you don’t know accessing your personal details.
Avoid sharing direct contact details on your profile. Even naming a specific town may be problematic.
Be careful with the contents of your profile picture and cover photograph as these are more likely to be publicly available.
If you children have Facebook profile, ensure their privacy settings are such that they can’t be directly contacted by people they aren’t friends with.