How can I hack a Facebook accounts?

You cannot go about and hack a Facebook account right away. The same is the case with hacking a facebook group or anything related with Facebook. Any Facebook hacking tool, program or script you might find online are purely fake and are often infected with trojans which steals all your passwords. Hence you should never use such programs. Below I will list some common ways you can hack facebook accounts successfully.

Remote Administration Tools-Remote Administration Tools or RATs are programs that gives you complete access over a target's PC. Some commonly used RATs are DarkComet and CyberGate, the first one being free and the second one, paid. Once your victim is successfully infected using your RAT program, you have entire access over their PC. Then you can use inbuilt features like Keylogger to record his keystrokes. So while your victim enters his password to login to his Facebook account, you can easily log it and use it yourselves. 

Java Drive By or JDB -A Java Drive-By or JDB as it is commonly known, is an ingenious and fairly new technique to infect people. It uses the technique of prompting unauthorized downloads on a target machine, often using a Java applet. So when a user visits the JDB link, he is often prompted with a Java dialogue box which on accepting, automatically downloads any program to his computer. So you can upload your RAT file as a file which will be downloaded by your target and hence, you can infect his PC and proceed like in the above step. 

Keyloggers -While RATS give entire access over the victims PC, Keyloggers are solely for recording the keystrokes of a victims PC. They are often more effective than a RAT in terms of keylogging with advanced features even mailing you the recorded keystrokes. If you do not want to go about setting RATS and finds it hard for you, keylogger is the solution. It is often much easier to set up and usually more effective.

Social Engineering -This is one of the most efficient but most underestimated method of hacking Facebook accounts. Social Engineering refers to the act of influencing your target into achieving personal gains. In this case, we will hack Facebook accounts. I will not be teaching you how to do it but it is fairly easy to do it on your own. One example is using a fake mailer like Emkei that lets you send a mail to anyone from a different From address. You could send a mail telling there's a security problem with their account and tell then to reset a password to something inorder to overcome the situation. And as the From address, you could use something like support@facebook.com to fool your victim. This is a simple example of social engineering you can use. There are no limits to the capabilities of Social Engineering.