I've been wondering about this for a while. When I make contact prints for 35mm and 645 negatives, what is the correct exposure (of the paper)?

I typically make it so that margin of the negatives, the transparent part of the negatives, shows just a little. That is, edges of the film clearly show but transparent part is barely showing. Is this correct?

It seems to me, if I expose more so that transparent part of negatives and margins of paper (out side of film) are equal in darkness (completely black), it's too far exposed. If I expose it less so that transparent part of negatives are clearly less darker than margin of paper, then it's not exposed enough.

Is this correct? What would be the most valuable way to expose it so that I can use it as a guide to make rough judgement for my final prints?