Order Communications
I have been speaking to some of my friedns about this, HOW DO THE ORDER COMMUNICATE WHEN EVERYTHING IS BEING WATCHED?, i am 75% percent sure that i have worked this out, browsing on JK's site, i read the rumors section and read this:
Think, "by an order member", i think it could be the two way mirrors, sirius gave one to harry before he went back to school and dumbledore said they have better means of communication than the fire in umbridges office. This is wat i think anyway, it seems to be the only reasonable thing ive come up with so far!