When creating a game name, put something like "Nerfed Guild Members Only pls", that is, if you keep the game open with no pwd. Of course, any non guildy friend of the host could join without the pwd so a label would be nice.

I was playing on Fnord today and when joining a normal looking game (no special title), I was asked if I was <insert name of guild here>. I said no and was promptly booted. No big deal. Guilds should be able to have their own private games. I'm just suggesting that if the game title indicated guild members only then no one's time is wasted.