Do a search on vgtact for posts by Aruspex. Basically each time you win a parley you earn a small amount toward your next skill point. You also earn a small amount toward your next presence point with that station.
So if you win a parley against a soldier, your soldier presence goes up and your diplomacy skills goes up. You may not see it because you haven't moved them far enough yet to earn a point, but they are moving.
It shouldn't take more than 12 successful parleys against the same station to earn a point of presence. If it takes you more than 12 wins to get a point of presence then please post the details of which NPCs you are parleying with, in which city, and what station and levels they are in this thread:
http://www.vgtact.com/showthread.php?t=2344
Also, if you by chance come across an NPC that gives you presence in the wrong station, or an NPC/Conversation Type that gives the wrong Prestige, please note that in the bug forum over at vgtact.