How does one obtain a publishing agent?
The whole process takes time and a very thick skin. Just keep at it. If it's something that deserves to be published you'll eventually find a publisher. Stay away from the major publishing houses. They will not even touch a manuscript that doesn't come from an agent they already work with.
Unless you have something really outstanding, be prepared for many, many rejection slips. If you find someone who will take the time to offer criticism, listen to it. They know what they're talking about. Just put your ego in a #10 paper sack and go for it.
Hope this has been of some help.