How does one discern a calling to the vocation of priesthood? Approaching this from a Catholic perspective, what are good signs that God is calling you to the vocation of priesthood, in other words, what must one look for to know whether you are called to the priesthood?
My own pastor has shared stories that he knew at a young age that he was called to the priesthood. As a young boy of 8 or 9 he says he "just knew" which is in keeping with a seed planted by God for the vocation. Oftentimes, young boys who are part of church-going families will mimic the parts of Mass and that is something that shows their interest. Of course discernment is an on-going process and once such a boy becomes a teen, it is best for him to be able to further his discernment through connections with a seminary professor etc. In the meantime it is always important for Catholic families to help their children know about consecrated vocations. They can do this through wonderful books and positive conversations meant to show all the ways that God might be calling. 

Other times a young man or grown man will feel a tug at his heart to become a priest. Again it seems to be God initiating the process but it is important for all people to be open to "hearing" God which is why studying Scripture and spending time with at least some like-minded friends will help each of us be able to see and follow the movements of God.

There was a time when discernment wasn't really part of the process to become a priest--when just about every Catholic family had a priest from its members; but times have changed and it is being seen more as a "call" and the depths of the vocation are better understood for today's men pursuing the priesthood.