I got into WoW maybe in Mid-march, I understand the hate towards the game, trade chat is full of retards and 12 year olds. However the game itself is easily in a class of it's own for MMOs.
Anyway, for tips, research addons for your class, you'll want something called "deadly boss mods" regardless of class, it'll help a lot.
Pick a reasonable beginner profession, don't go with Leatherworking, Blacksmithing, Tailoring, Engineering as a beginner, it requires a lot of time and in some cases money. I'd go with Jewelcrafting, Alchemy and other such professions, I'd read up about them to get a better grasp on them, make sure you check if your profession requires a gathering profession to go with it(like Jewelcrafting will require Mining as a new player) otherwise you will not be able to afford to level it.
Make sure you level up your Cooking/First Aid/Fishing as you level! Cooking gives valuable stat food endgame and Fishing gives fish required for some foods.
Understand what stats do for your character, Hit, Expertise, Parry, Dodge, there are hard caps for these, so again, check what they are so you don't go over with them and waste gem slots etc.
Research your class in prep for endgame, look on youtube for boss video guides and such, Tankspot do the best ones.
But yeah, doing your research is fairly important, namely with raiding.
