Password cracking is a fundamental hacking and digital forensics skill. Nearly every system is authenticated by the traditional username and password and even if two factor authentication is used, one is usually a password.
Cracking passwords can take many forms. See my article of password cracking strategies before you embark upon password cracking. It will likely save you significant amounts of time.
6. Creating a Domain Specific Wordlist with cewl
7. How Elliot of Mr Robot cracks Everyone's Password
For Wireless (Wi-Fi) Password Cracking, check out my Wireless Hacks series.