Claims investigations are often described in terms of services: surveillance, background, social media, canvass, recorded statement, scene investigation. Those are methods. They are not objectives.
Before choosing the method, write the question the evidence needs to answer. If that question cannot be stated clearly, the assignment usually needs more development.
Match the method to the evidence gap
Background and public-record research can develop identity, addresses, business relationships, or affiliations. Open-source research can identify publicly available activity indicators. Pattern-of-life research can help develop recurring locations and timing. Interviews develop firsthand accounts. Surveillance documents observable activity. Each method solves a different problem.
Sequence matters
Sometimes research should precede field work. Sometimes a witness statement should precede surveillance. Sometimes the available information is already enough and no additional investigation is warranted. The strongest strategy is not the largest assignment; it is the smallest proportionate plan that can materially improve the decision.