1. Use of Strong Password : You have to make a strong password and which is not use for any other account. For other accounts use different passwords. Use a different combination of numbers and letters and also use logical operators like (@, ! or &) etc. You can use online password generators to generate strong passwords.
2. Activate All Security Settings : Make secure your email accounts like Gmail, Yahoo etc. with the help of two step protection. If connected email is secure then your have to do some security settings in Facebook account settings. Go to Facebook Settings -> Then Switch To Security Settings. Always add at least 2 email address and mobile number. Try to use and activate all given security settings available in security section like secure browsing, Log in Notification, rusted Contacts and more.
3. About Section Settings : All your personal information is in about section that what is your mobile number, where you live, where your family lives, your date of birth, your work place and everything you put in there. So keep your information secure from unknown persons and keep them only Friends or Only Me.
4. Privacy Settings : From privacy setting you can manage who can see your stuff. Don't let unknown persons to see your stuff keep them only friends can see your posts. You can also manage who can look you up. If you allow anyone can look you up then any random or unknown persons can search you on FB. Keep only friends can look you up, so you can keep far yourself from other persons you don't know.
5. External Links And Apps : Never click on any doubtful links which can send by your friends or any other company and want you to put your email and password. Also check URL before login into FB, Sometimes people make fake Facebook Log in pages. If you see any doubt in link then get change into www.Facebook.com. Always make sure that log in Facebook page URL must contain Facebook.com. If you URL or link is differ then leave that page. Never log in into any Facebook app which is not trusted at all. Never enter password in any application.
6. Update browser : Update your browsers because latest version browsers become with new security protection facilities which will alert your from any harmful sites. FB mostly prefers Mozilla, Google Chrome, Safari, opera and Internet Explorer.