Well, if its your server you have to take care of a right advertising, you could start right here, creating a good thread with details of your server, pictures of it, full information and it might attract people. Also you could use otservlist.org, not necessary highlighted and that's the way should work.
Ps. Gamemaster position is nothing related with advertisement, its a person that knows about your server and that he can answers all the questions asked by the new-old players, they take responsibility of your server while youre not there. So I think you should change your title for "Who can help me advertise my server"