Conducting preliminary research should be done prior to any surveillance efforts.
Research should include background data, case pertinent information, residential and vehicle identification, photo (if possible), social media search, address history, relatives data, criminal history, legal history, phone numbers (if possible), employment information, marital status, hobbies and interests, club memberships, and any other information you can obtain. All information can be used effectively in an investigation. Gathering facts will always raise confidence and more success.
Going the extra mile can make that needed difference in a case. Sometimes it is the little piece of extra information that gets you the answer. For example: A subject residence has been appearing empty for the first two days of surveillance. You just so happen to open a real estate app and you look up the address. Turns out the home was sold a week prior. You know preliminary data containing addresses may not be accurate to date. Now you can let the client know surveillance must be postponed until further information is obtained. So, you run a subsequent search a few weeks later and a utility was processed at a new address. Say you wind up getting great footage of the subject from the new location and the client wants another round of surveillance. A simple real estate app double the allotted hours from the client, thus earning you more money.
It‘s not all about money though! Safety should always come first, and proper research may prevent putting an investigator in a potentially dangerous situation.
Every case is unique, as every person is unique. The many factors that make a human unique, are the same factors that make each case unique, because in many cases the subject is a human. An investigator should never assume any information or outcome based on experience or any prior case. Experience should be reflected in decision-making ability but not presumption. If you are going to assume, then at least assume the worst. Then you can prepare for the worst and hope for the best.