Go Shadow until 60.
Again, go Shadow until 60.
A little searching will give you some good builds as well as places to level and/or grind.
This one gives a great Shadow build (technically 2) to 60: http://forums.worldofwarcraft.com/thread.html?topicId=12021216&sid=1
And this one is good for locations to level grind for Alliance: http://www.calloffate.com/forum/forum_posts.asp?TID=37911&PN=3
So far, I've primarily followed these guides for my leveling. For professions I've chosen Herbalism and Alchemy. Since Alchemy requires purchases of recipes, materials etc., I've held off and primarily concentrated on fishing and herbalism. The fish and herbs that I've gathered have assisted greatly in my pursuit of riches. Combined with a stingy attitude towards the Priest gear in the Auction House, I also use Auctioneer http://www.curse-gaming.com/en/wow/addons-146-1-auctioneer.html
to sell every green, blue and material that I or a guildie can't immediately use. I've been able to amass quite a bit of gold for a level 42 (app. 175 G at the time of this writing). Farm a lot and hold off on raiding for a bit. The reason being, once you spec holy/disc for groups, your dps will go down a lot and farming/earning gold may not be an option unless you've learned some nice enchant/alchemy recipes that you can use to sell high level potions and enchants. I hope to eventually purchase my epic mount, then earn 1000 more gold.':shock:'
In general, you'll need to learn to take care of yourself around mobs when your soloing. Because if the Priest knows how to survive, your future teammates will be happy. Once you've learned to take care of yourself, you can learn to take care of others. So instance... a LOT. MOre practice healing while shadow specced will only improve your healing abilities when you finally go holy/disc. Starting out, you can only team with up to four others. Working your way up to 39 others is going to take some practice. To be honest, I'm a little scared of all the health bars that I'm going to see in someplace like MC or BWL. But once you've learned to estimate the heals that will sustain a player, you'll start to realize that you don't need to keep them at full health.
Ooh! and try to use HoTs (Heals over time). Like burst damage, nothing aggros more mobs than a 1113 hit point crit heal in Scarlet Monastery or Uldaman. They really get mad when you keep the rogues and warriors alive.
Well, that's it for now. Please feel free to shoot down my theories or ideas or add some ideas of your own. Who knows, maybe Noen will sticky this and we'll start a whole new trend of Class forums.
GET TO 60!