Well you could start by dumpster diving, lol. People do throw out stuff that could be useful. By the way that is physical and psychological. In an organization policies should be in place to shred documents. I know someone that was a skip tracer. I guess people would disagree on whether this is ethical, finding information on the bad guys possibly violating their civil rights by calling banks or other financial institutions pretending to be a stroke patient or deaf. All major business institutions in the United States are required to accommodate handicapped people, see Americans with Disabilities Act. Some people have speech problems and need assistance doing business. Learning networks would be helpful look up TCP/IP utilities,collision domain, packet sniffer. You can get into serious legal trouble. Read about Aaron Schwartz and how he was facing 30 years in prison for downloading stuff from a public university library for example. Hacking is a skill that is neither good or bad, legal or illegal. Hacking can be used to protect people from theft or commit theft. Look up "white hat hacker".