Gamemasters can be reached through the in-game petition system by pressing the escape key and selecting your petitions button. Alternatively, they can also be reached on the eve online website under the support section. You may even be messaged by a GM during your free trial period, to answer any questions that you may have about the game during your first days in New Eden. The greeter Gamemasters, when appearing in game, will always have text highlighted yellow in chat channels, and will always have the prefix "GM" in front of their name.
A Gamemaster, when appearing in game, will always have text highlighted red in chat channels, and will always have the prefix "GM" in front of their name. Any character which does not exhibit both of these traits is a impersonator and should be reported immediately via a petition.
It is reminded that impersonating a GM is against rule 8 of EVE Online Term of Service: You may not impersonate or present yourself to be a representative of CCP or an EVE Online volunteer.