As a postdoc, I'm considering to apply to research-only positions (for instance in a research institute, and not a university), and I know that one of the responsibilities of being a researcher is to recruit PhD students.
I personally only know people (including me) who have been "recruited" for a PhD by one of their teacher (usually at Master level), and so I wouldn't be sure of how to proceed in order to recruit a PhD student as a young researcher:
- Are there some specialized websites where to post ads?
- Is it better to contact some teachers to see if they have good students to recommend?
Moreover, in this case, which criteria can one use? If I were to teach, I would have a whole semester to know a student, and to decide whether it would make a good fit for a PhD, but how to do that during a one-hour interview?
PhD studentships are quite often advertised like "normal" jobs, i.e. on general job boards/recruting websites. If you have contacts, by all means use them. As for evaluating the candidates, similar guidelines as for evaluating applicants for any jobs apply. I don't think there's a one-fits-all answer. Note that the hiring process may also depend on what institution you'd be working for. They might have an HR department that screens/selects the candidates.