What information should an investigator gather before conducting surveillance on a suspect?

The most critical information an investigator should gather before conducting surveillance on a suspect is their daily habits and routines. Understanding these routines allows the investigator to plan surveillance effectively, identifying optimal times and locations where the suspect is likely to be observed. This information can include the suspect's work schedule, frequent locations, and patterns of movement, which are vital for the success and efficiency of the surveillance operation.

While the other options—financial status and family background—can provide context about the suspect and might be useful in broader investigations, they do not directly influence the practical aspects of conducting surveillance as much as daily habits do. Financial issues may offer insights into motives but are not necessary for planning surveillance tactics. Similarly, while knowing a suspect's family background can be helpful in understanding their social context, it does not directly impact the logistics of surveillance.