Go do a search for different cargo airlines on the forums. I am also interested in flying cargo in the near future once I finish my ratings and build some time. I have learned allot about different carriers that I both new of and have not known of. So I feel that when it is time for me to go find a freight job I will have an idea of who to go to and who not to go to. And as people have posted above, meeting and getting to know everyone you can will benefit you greatly, if you are friendly and kind to people they will remember! Flying freight is a good business to be in!
Good luck!! =)