OK, questions has been asked many times.
Here is what you do while leveling:
Do Battlegrounds, as A) It gets you honour but B) It now gets you experience points for completing objectives which means your "killing 2 birds with one stone" as the expression goes.
DO NOT spend your Honour Points whatever you do. Wait until you get to level 80. Even when you get to level 80, do not spend them, as you wont have nearly enough for what you need.
Once you reach level 80, there are several things you need to do. Firstly I would suggest not going to BG as you will get destroyed. Instead doing your HC's and getting PvE gear. Once you have decent PvE gear, you can start doing things Like VoA which allows you to gain your PvP gear. Also with decent PvE gear you can half decently play PvP BG, although with no resilience you are bound go get done.
Once you have accumulated the Honour Points you need, start buying your PvP gear. First of, you want to get the set bonus that gives you 100+ resilience, this is two items. If you want to do PvP you need to get this quickly, therefore you need to get the cheapest two items, (normally shoulders and hands if I remember correctly). Once this is done you are good to keep adding, once you have your 100+ resi, you'll find it much easier to do PvP but not that wrathful gear is out, our still going to struggle.
Additionally what you want to do is gain Sons of Hodir reputation to allow you to get the head enchant for when you get your head.
REMEMBER: Always gem and enchant your itmes with the best you can possibly get as soon as possible.
It sounds like you're looking for a restoration (healing) spec. The classes capable of healing are druid, monk, paladin, priest, and shaman. Racially there aren't a lot of significant differences, though specific races can only play certain classes. (Alliance races are listed below as well, though the original question was about Horde)
- Druid (Horde: tauren, troll; Alliance: night elf, worgen) - limited to leather armor; tree form (cooldown ability) increases healing throughput; good profession choices: skinning/leatherworking, herbalism/(inscription or alchemy), mining/jewelcrafting
- Monk (any except Horde: goblin; Alliance: worgen) - limited to leather armor; use brews and teas as the primary basis of skills; similar professions to druid (I've never played a monk healer, so can't really address the specifics...)
- Paladin (Horde: blood elf, tauren; Alliance: draenei, dwarf, human) - can train to use plate armor at level 40(?), limited to mail previously; some people think they are limited to single-target (tank) healing, but do have some raid utility too; professions: any of the combinations mentioned above, or mining/blacksmithing
- Priest (Horde: any except orc; Alliance: any) - limited to cloth armor; best professions: tailoring/enchanting or herbalism/alchemy
- Shaman (Horde: goblin, orc, pandaren, tauren, troll; Alliance: draenei, dwarf, pandaren) - can train to use mail armor at level 40, limited to leather previously; can also use shields; in addition to direct healing spells, also have totems that provide passive effects and healing; professions: similar to paladin
For all, you can learn first aid, cooking and fishing as secondary professions that will come in handy.
Note that resto is much easier to level as primary spec now that you get access to the LFD tool at level 15. And, they're in big enough demand that you shouldn't normally have queue times that are very long.
ETA: Cataclysm/Mists updates
Best Answer
I think what you need to realize is as far as PvP purposes go, you need to decide one of two things.
First off is what is your play style?
-Are you a stand in one spot and dps or kite the enemy and keep on your toes player?
-Do you prefer to be able to kill the enemy as fast as possible, or sit back and do a steady amount of damage but have a much higher survival chance?
Each option provides it benefits, and this is true for the stats as well, PvP Power increases the amount of your damage that will break through the enemies Resilience. Given all players start off with 40% Resilience now naturally, PvP Power will give you the highest survivability in the short term as you should be able to outdamage another player.
In the long term you need both, one will reduce the amount of damage you take and the other will increase the amount of damage you do. Again, stat prioritization is greatly dependent on you and how you want to be able to dish out and receive damage in PvP.
Simply put, if you want to take less damage, get Resilience. If you want to do more damage, get PvP Power.