The search methodology and collecting compromising evidence come down to several directions.
One of the first is the installation of covert surveillance of a person in order to search for fresh compromising evidence on a person from everyday life, that is, these are people, places that the object visits and the very behavior of the object.
The second direction is the collection of information about the object from various sources such as the press, the Internet, various databases.
The third direction is the use of various operational combinations and techniques, for example, the search for ill-wishers among the environment of the object in order to obtain information of interest from them. They also use the technique of a fake artificial situation to obtain compromising evidence.
Whatever else humanity would come up with ways to get compromising evidence on the face. All of them in one way or another will be reduced to the above listed.