I started WoW a month ago, here are some stuff I found useful fand some random newbie thoughts
1. Download the Quest Helper addon, it has an arrow showing you where to go to complete the quest and turn it in. With it you can do all the quests in an area and do one massive turn in and saves on the whole running around thing.
2. Get bags asap so you don't have to keep running back to vendors to sell the junk, saves time.
3. Pick at least one gathering profession in order to make money for your first mount. I'd recommend skinning since you can skin any beast you kill, the other can be herbalism, mining or whatever is useful for your class.
4. Save $$ for your first mount at lvl 20
5. Hunters are insanely fast and easy to level, pretty fun as well. There is literally no down time once you get Aspect of the viper which regenerates mana and you have reliable crowd control with your traps. And pretty much any beast can be tamed and be your pet. Hunters seem to be able to solo everything.
6. Warlocks are more fun to play but are way more delicate and kill slower at low levels. And fear seems to be totally random and feared mobs seem to always bring back friends >.>
7. I just made a Unholy Death Knight tonight (yes I do like pet classes), seems to be fun so far.
8. The 2 newer races, blood elf and draenei look noticeably better, especially their females :3 I'm in love with the draenei and their instant heal over time spell. If only I could make a draenei warlock >.>