Hey this is Musashi here today with your basic leveling tips for newbies to WoW. This post assumes you know how to do basic things (get around,accept quests,read the quest log if your stuck etc.)
Step 1. gather all the quests you can in the area you are leveling in.
Step 2. Do all the quests in an area (e.g. if you have to collect some headbands from the defias you have to kill for another quest do them at the same time) and finish them before heading back to the quest reciver location (for my example in sentinel hill)
Step 3. Repeat till your done all the quests in the area.
Now here comes some other basic tips for questing. Try to do them alone. You get much more XP per kill when your alone. If you have those tough group quests try to do them with a group around your level. If that fails ask a higher level to help you. When it comes to instances always try to keep to the same rules(minus of course doing it alone). I personally try asking my fellow guildies when I'm leveling an alt if they are not busy if they want to help me out by running me through an instance (this becomes less common the higher you are, don't try asking for a run through BRD unless you really need to do it for quests.)
Now here comes this point in which I hope you will take the most from this post. Spec your character accordingly. If you don't get to do instances often, don't spec Prot. on a warrior, Instead spec fury up till lvl 40 than choose either between Fury for dualwielding or Arms for two handers depending on your play style. If you aren't sure what is the best leveling spec, ask on the community site's class forums or ask in game. Dont forget your "P's and Q's" they go a long way to getting a useful, and considerate, answer from people. Don't Spam the chat channels either with macros. they get you ignored and you will end up hated by your server and still being a lowbie.
I hope this post helps people level their alts faster. I'll try to post something tomorrow, no garuntees or promises, school comes first for me. cya!