Investigation techniques are methods used to gather information and evidence in various fields, such as law enforcement, research, and corporate settings. Common techniques include interviews, where investigators ask questions to gather firsthand accounts, and surveillance, which involves monitoring activities to collect data without direct interaction. Another important technique is forensic analysis, where scientific methods are applied to examine physical evidence, such as fingerprints or DNA. Additionally, background checks and data analysis help investigators uncover relevant information from records and databases, aiding in the overall understanding of a case or situation.