Just setup an in-game advertisement that repeats itself every 5 minutes or so. People will get it eventually and in time regulars will just help other new players.
[PGNBBS.CSProject.Org] Don't forget to add pgn1.csproject.org to your favorites! Thanks!
When I first set it up on my servers. I randomnly join my server and ask for the server's ip. First few weeks they keep telling me to just click on Add in the server list. But now most of them just say, wait for the server advertisement or go to their bulletin board.