first of all: dont expect to walk into heroics when you reach 85.
(1) wear a tabard, and mine the normal modes till you get (as a minimum) 333 gear accross the board.
(2) as you do normals, you will pick up some nice 346 gear with JP accumulated, or with faction gear (as you get rep).
(3) keep on top of dailies in factions to get nicer gear and enchants. Rinse repeat for a few days, you reach revered in all.. then you will get a nice selection of gear ready for heroics... and being useful in heroics.
(4) better still, by farming in normals.. you also have the advantage of not being a burden to the community (ie: being a window-licking moron that so frequent this game atm)
(5) when you can do the random heroic.. do so.. and level your professions... get some nice epics crafted from chaos orbs dropped inside.
(6) rinse repeat......
(7) fall over, die, get back up
(8) pay monthly subscription
(9) rinse repeat