The Talents

Combat is the tree to go deep if you want to level fast. However for levels 20-24 you can not pick DPS talents in the combat tree, so I suggest you to take a little deviaton into the Assassination tree until level 35. Then unlearn your talents and throw everything in the Combat tree.

Level 20-24: Malice
25,26: Remorseless Attacks
27,28: Murder
29: Ruthlessness
30: Relentless Strikes
31-35: Lethality

So, at level35 your talents should be like this.
The only point not spent in DPS talent is Ruthlessness. You could have picked Improved Eviscerate(1/3) at level 29. However, 5% increase of 10-15% of your total damage(Eviscerate will do even less) is not noticable at all. With Ruthlessness 1/3 you will get a combo point for every 1 out of 5 finishers. This is not much but combined with Relentless Strikes will stimulate you to do 1-2 combo points finishers more often. Combinations like Sinister Strike x2 Slice and Dice or Sinister Strike x2 Expose Armor will sometimes reward you energy and combo points. I use such combos against mobs of my (or higher) level, mobs with high armor and named mobs. Expose Armor adds damage for every hit you deliver (improves your white and yellow damage). Slice and Dice improves only your white damage, but with it you will score more Poison procs. If you use two Instant Poison Slice and Dice is a huge DPS boost.

Use Expose Armor/Slice and Dice combos only against high armor/strong opponents. For normal mobs revert to the normal strategy. Charge in, several Sinister Strikes + Eviscerate. IF your Eviscerate did not kill the mob and you got extra combo point from Ruthlessness, if you feel the mob is dying any moment you can use Slice and Dice(SnD) and immediately jump into another mob while SnD is active.

Remorseless Attacks is a great DPS boost. Exrta critical strike on your first Sinister Strike(SS) is great, and with it SS will do over 30% of your total damage. And it will keep you running fast between opponents because you will always want to get the Remorseless bonus.

At level 35 or 36 unlearn you talents and spend everything in Combat. If you are 35 get 5/5 Sword Specialization and then 5/5 Dual Wield Specialization at 36. You should be using two Swords now. Sword of Omen is the best you can get at level36. Use it in the main hand and buy some fast sword "of the monkey" from the AH for your offhand.

Also you have learned Riposte. You can use it after you parry opponents strikes. It deals nice damage will disarm your opponent if he uses a weapon. You can bind it to a key, watch for parries and use it manually, or you can use a macro. A macro like
/castrandom Sinister Strike,Riposte
will randomly do one of them. Its not a perfect solution, you will have to mash the button with this macro alot not to waste an energy. Its up to you. Riposting manually is still good, you just have to watch for those parries.

Legionnaire's Sword vs Stinging Viper: Low level Battlegrounds

At level 18 or 19 you can use one of these:

Legionnaire's Sword

Stinging Viper

They are almost the same. The sword is reward from doing Warsong Gulch and the mace is a drop from Lord Pythan in the Wailing Caverns. Which is easier to get depends on your luck. I prefer the sword because it is guaranteed you will get it when you get enough honor and marks. 10 Warsong Gulch wins is enough to get it. The problem is you get rewarded honor once every day, in the night (around 3am i think). So it is not a bad idea to visit Warsong Gulch several times between levels 10-18. I went there at lvl13, stealth leached all the honor and marks i needed and got it the next day when i hit level18. People will complain about you being too low level in Wrsong Gulch, just ignore them. It is a war out there.

The mace may be easier to get but you need to be lucky. While it can drop on the first run, you may need to go to the Wailing Caverns several times which may be long.

I told you that the most important thing is to level fast. A good mainhand weapon may double your experience per hour and even better, it will make it more enjoyable. So the time spent in Warsong Gulch will pay back once you hit 18. Get 30 marks and 300 honor(just to be sure you wont have to wait another day). It will serve you well until late 20s.

Level12 - Swords from The Crossroads

In the Crossroads, look for the Weapons Vendor Nargal Deatheye.

He sells the following green swords.
Enamelled Broadsword - 12-23dmg +1strength 2.40speed for 28s78c
and
Feral Blade 12-24dmg +1agility 2.60speed for 24s7c

These weapons are Limited Supply, if they are not there you will have to wait. Do a quest, come back in 5minutes. Enamelled Broadsword is the better choice obviously. It has better dps and almost the same damage range. This is an example when faster weapons are better. But Feral Blade is good too. You can only use one of them because they both are Main Hand.

Make Crossroads(XR) your home, get all quests and start doing them. Do the plainstrider quest and Disrupt the Attacks, go back to XR, turn them in and get next part - The Disruption Ends. When done turn them in, get new quests and head to Ratchet (a bit southeast of XR). Again get all quests and don't forget to click on the Wanted: sign, it will give you the baron quest. Do all the pirate quests and kill the baron when you are 14. Turn quests in, heart to XR and take the road west(northwest). In a bunker there you will get two quests to kill centaurs. Do them alongside with oasis, mushrooms and zhevra quest. This is how you must stack quests. Turn them in the XR get new ones and you know what to do. The Barrens has enough quests to keep you going beyond lvl20.

At levels 12,13 and 14 pick Improved Gouge. I like gouging a lot. You control the opponent, get extra rage, swing time and combo points. At 15-19 pick Precision. It is a huge dps boost.

Sometime after level16 when you are in Orgrimmar to learn new skills get the quest Find the Shattered Hand. It is a chain of quests that ends in Ratchet and allows you to learn and level your Lokcpicking skill. Around level 20 when you are near Ratchet do the final part. You get Thieves' Tools and E.C.A.C from Wrenix's Gizmotronic Apparatus and go inside a ship near the pirates. When you click the treasure a parrot will spawn. Immediately use your E.C.A.C on him and he will turn into smaller polly and kill him. The ship is at 64,45. You can skill up your lockpicking up to 5 times your level. Better spend the time to do it.

Notable quest rewards:
Hezrul Bloodmark reward: Bounty Hunter's Ring
Stolen Silver reward: Rambling Boots
Serena Bloodfeather rewards: Elegant Shortsword and Harpy Skinner