How can I prevent hackers from going into my personal information on Facebook?

Don't put any information you don't want anyone else to have. Security is up to Facebook, nothing you can do except to use a Secure password.

Yep, don't put anything personal on there, only post what you will post publicly.

Facebook security settings and polices are at best a moving target. Nothing you pt of Facebook could be considered private or secure. Also use a strong password and change it often.