Here is what folks have previously said on the other forums.
"Check out http://us.battle.net/wow/en/forum/topic/6863526914 for general Challenge Mode info, and Challenge Mode Gold run guides; or search for runs on YouTube to get a general idea of the instances.
General requirements are Buff consumables (Stat food, Flasks, Stat Potions), as well as Lesser Invisibility Potion / Invisibility Potion when pushing for Silvers/Gold, voice communication, and some time to dedicate to the runs. If you're pushing for Silver or Gold, it might take some time. Just be willing/able to give it your attention for a while.
When posting to look for a group, mention a few things.
Horde or Alliance
Times when you're available
Which instances / Medals you're looking for
Experience in Challenge Modes / other creditable things
An armory to the toon you plan to run with (If not posting from that toon)
Don't be afraid to add people from the thread and make your own group! They won't bite, I promise.
After all, someone has to be the guy or gal to start invites.
Good luck to those still finishing up, and to those here who are just starting."