Currently, I am in the process of finishing my PhD and starting a PostDoc position. Part of this position will be the supervision of Master theses. 

I have little teaching experience, and no supervising experience except for "passive" experiences of being supervised myself when writing a Master's thesis myself. An added difficulty is that my workplace and the university where the students are studying are 150 km / 2 hour train ride apart, so I can't just have "open office doors" and meetings have to be pre-arranged. 

What frequencies of meetings with students under supervision do you find helpful or too much? This will surely depend on the student, but how do I figure out what is right for a student I have never met before?