ok, so here is some nice, easy-to-read shadow guide which i think should be nice for beginners (not sure if its much upto date, but for lvling should be more than enough): http://www.mmo-champion.com/threads/...leveling+guide
but tbf leveling priest is so much fun, id recommend you just read the tooltips/talents and decide yourself, give it a little twist, experiment, go wild
Disc to 40 or 50, Dual spec to Shadow when you can. Start using shadow for questing probably around when you get Vampiric Touch. Use Disc to heal dungeons for instant queues.
Use standard glyphs except for these 2 which are amazing for questing
- Spirit Tap (regen mana after a kill)
- Psychic Scream (mobs do not scatter when you fear them, so you can use your fear liberally and not end up aggro'ing everything in the radius).