Sorry, no wmw triad here, I'm in a mwm vee.
It's true what bookbug said, you don't want to put too many eggs in the triad basket, leave room for the possibility that you (too) could end up in a vee configuration or something like that.
There's really no "standard rules for triads" that I know of. I mostly just know of the mantra for all polyamorists: "Communicate, communicate, communicate." Since I see communication as an art form that would take about a million years to master, I feel safe to say that you'll have opportunities to get better at communicating throughout your life. So get lots and lots of practice. And practice your listening skills too. Listening is actually the most important part of communicating (I think).
As it says in Sex at Dawn (the softcover edition),
"Every person is a world and every relationship a universe."
-- Sex at Dawn, p. 314
With that in mind, you should know that what will work for your triad (or vee or whatever it is) will be completely unique. Some people need lots of rules (at least at first), others can just let intuition be their constant guide. And everything between. If you do need rules, talk with each other and decide what they'll be. And renegotiate periodically. Talk about your wants, needs, and boundaries with each other. Oh and don't try to rush anything too fast. Small steps is the best way to go, usually. I guess with the girlfriend living in a different State that definitely slows things down. Will the three of you ever live together someday, do you think?
I hope your August meet-up goes well.
Sincerely,
Kevin T.