Do note this is only a portion of the patch notes from season 2

v1.0.0.129 - 2011-11-15

- Twin Disciplines

o Initial spell vamp gained upon obtaining 10 bonus attack damage reduced to 8% from 10%

o Additional spell vamp reduced to 1% per 6 attack damage from 1% per 5 attack damage

o Initial magic damage bonus upon obtaining 20 ability power reduced to 8% from 10%

o Additional magic damage bonus reduced to 1% per 6 ability power from 1% per 5 ability power
- Mark of the Assassin

o Projectile base damage and proc base damage reduced to 45/70/95/120/145 from 50/75/100/125/150

v1.0.0.123 - 2011-08-09

o The cooldown before Akali's next Shadow Dance charge and her current stacks are now shown in the same buff

v1.0.0.121 - 2011-07-08

o If Akali uses Shadow Dance on a champion, she will attempt to attack the target upon successfully arriving

* Twin Disciples
Twin Disciplines consists of two parts. Once Akali has 19.5 or more ability power from runes, masteries, and/or items, her basic attacks will deal 8% bonus magic damage plus 1% for every 6 ability power she has. In addition, once Akali has 9.5 or more attack damage from runes, masteries, and/or items, she gains 8% spell vamp plus 1% for every 6 attack damage she has. The two parts of this ability are independent of each other.
Discipline of Force formula is: If Akali has more than 19.5 ability power, then the percentage of attack damage converted to bonus magic damage is equal to "Ability Power minus 19.5, multiplied for 0.1666, plus 8". [(AP−19.5)×0.1666+8]
Discipline of Might formula is: If Akali has more than 9.5 bonus attack damage, then the spell vamp percentage is equal to "Bonus attack damage minus 9.5, multiplied for 0.1666, plus 8". [(Bonus_AD−9.5)×0.1666+8]
The bonus magic damage done from Discipline of Force does not affect towers. But it will affect inhibitors and the Nexus.
The innate will take any temporary buffs to those stats when calculating the stats gained into account. Of course this increase on stats will be temporary too.
The bonus damage from Discipline of Force will not break spell shields.
The bonus damage from Discipline of Force will not proc any slow from Rylai's Crystal Scepter.
The bonus damage from Discipline of Force will not benefit at all from Akali's Spell Vamp.

* Mark of the Assassin
(Active): Akali throws her kama at a target enemy, dealing magic damage and marking the target for 6 seconds. Akali's melee attacks against a marked target will consume the mark dealing the same magic damage again and restoring energy.
Cost: 60 energy
Range: 600
Cooldown: 6 / 5.5 / 5 / 4.5 / 4 seconds
Magic Damage: 50 / 75 / 100 / 125 / 150 (+0.4 per ability power)
Energy restored: 20 / 25 / 30 / 35 / 40

Mark of the Assassin is a targeted spell that deals magic damage to a single target and marks it for 6 seconds. Akali's next basic attack against the marked target will destroy the mark, dealing the same magic damage again and restoring some energy to Akali.
The mark effects won't proc if the attack is dodged, missed or blocked by Aegis Protection. (
It has a very brief channel time (0.1s) upon cast before activation.
Mark of the Assassin placement will be blocked by spell shields. But the mark's detonation won't.
Mark of the Assassin will damage Black Shield, but it will block neither the mark's placement nor the detonation.
Mark of the Assassin will benefit from 100% of Akali's Spell Vamp.
Both the placement and the detonation will proc Rylai's Crystal Scepter 35% slow for 1.5 seconds after activation.
The mark's placement won't activate any On-hit effects. Given that the detonation is proc-ed by basic attacks, the same basic attacks that detonate the mark will be able to proc On-hit effects.
The mark's detonation doesn't count as a spell cast for any purpose.
The mark will not detonate if Akali hit's the target while blinded.

* Twilight Shroud
Akali throws down a circular cover of smoke that lasts for 8 seconds. While inside the area, Akali gains armor and magic resistance and becomes stealthed. Attacking or using abilities will briefly reveal her. Enemies inside the smoke have their movement speed reduced.
Cooldown: 20 seconds
Range to center of AoE: 700
Radius of AoE: 300
Cost: 80 / 75 / 70 / 65 / 60 energy
Armor and Magic Resistance Bonus: 10 / 20 / 30 / 40 / 50
Movement Speed Reduced: 14 / 18 / 22 / 26 / 30 %

Twilight Shroud is a circular Area of Effect ability that will appear on the target area and last for 8 seconds. The Area will slow any enemy units that pass through it. In addition, Akali gains additional armor and magic resistance while on the circle. If Akali is inside the circle she will be stealthed when not attacking or using abilities, revealing herself if she uses any abilities or her basic attack. If she stops attacking the stealth buff will return half a second after.
If Akali becomes unstealthed, she still retains the armor and magic resist buff as long as she remains in the shroud.
Akali will stay stealthed for a short time after leaving the shroud.
If an enemy is slowed by Twilight Shroud and then is slain less than ten seconds after the slow wears out, Akali will receive an assist even if she didn't do any damage to the enemy.
It has a very brief channel time (0.1s) upon cast before activation.
Twilight Shroud won't be blocked by spell shields.
Twilight Shroud slow will be blocked by Black Shield as soon as it is protecting the target.
Twilight Shroud will not proc Rylai's Crystal Scepter slow as the shroud doesn't do any damage.

* Crescent Slash
Active): Akali flourishes her kamas, hitting nearby units for physical damage.
Cost: 60 energy
Radius of AoE: 325
Cooldown: 7 / 6 / 5 / 4 / 3 seconds
Physical Damage: 30 / 55 / 80 / 105 / 130 (+0.6 per attack damage) (+0.3 per ability power)

Activating Crescent Slash will make Akali deal physical damage to all nearby enemy units.
Akali channels for a brief time (0.2s) during which she activates the ability. That means that the cast animation is very short and Akali will be able to continue with her other attacks immediately.
Crescent Slash will be blocked by spell shields.
Crescent Slash damage will not be blocked by Black Shield.
Crescent Slash will benefit from 33% of Akali's Spell Vamp.
Crescent Slash will proc Rylai's Crystal Scepter 15% slow for 1.5 seconds after being hit.
Crescent Slash won't proc any On-hit effect.

* Shadow Dance
(Active): Akali moves through the shadows to quickly appear next to her target and deal magic damage to it. Akali gains an Essence of Shadow once every few seconds up to a total of 3, affected by cooldown reduction. The time to gain a charge doesn't count when at maximum charges. Additionally, Akali gains an Essence of Shadow for a kill or an assist.
Cost: 1 Essence of Shadow
Range: 800
Cooldown: 2 / 1.5 / 1 seconds
New Essence of Shadow: 25 / 20 / 15 seconds
Magic Damage: 100 / 175 / 250 (+0.5 per ability power)

f Akali has an Essence of Shadow, she can consume it to activate the spell. Shadow Dance will allow Akali to target an enemy, she will dash to what was the target's location at the moment of casting and will damage the target immediately after the dash.
Akali gains an Essence of Shadow over time (affected by cooldown reduction) or whenever she attains a kill or an assist. She can save up to three Essences of Shadow.
Akali will attempt to attack the target after hitting it with Shadow Dance.
The time to gain a charge doesn't count when at maximum charges.
Shadow Dance is immediately activated upon cast.
Shadow Dance will be blocked by spell shields. Akali will dash to the target's location but there won't be any damage.
Shadow Dance will damage Black Shield.
Shadow Dance will benefit from 100% of Spell Vamp.
Shadow Dance will proc Rylai's Crystal Scepter 35% slow for 1.5 seconds after being hit.
Shadow Dance won't proc any On-hit effects.

Pros:
- High Burst Damage
- Has an insane amount of burst damage.
- Can escape easily with Twilight Shroud & Shadow Dance.
- Covers vasts amount of distance with her sheer mobility.
- Attack animations allow you to farm easily.
- Extremely versatile.
- Snowballs if doing well
Cons:
- Higher learning curve.
- Needs specific rune page for her passives.
- Practically no crowd control. (Rylai's Crystal Scepter)
- Crowd control rapes Akali.
- Undoubtedly squishy.
- One of the first targets people search for.
- Items such as Vision Wards & Oracle's Elixir cripple her.

My item order is just a pretty basic.

Start Amplifying Tome and a Health Potion. Generally i try to stay in lane til i can go back to get Boots of Speed and Hextech Revolver. Then I rush into an early Sheen. After that i finish boots into either Sorcerer's Shoes or Mercury's Tread. Be sure to base boots off the enemy teams amount of CC(crowd control). If they have a relatively low amount of CC then get Sorc's, but if they have a pretty decent amount of CC go for Merc's. Then once boots are finished being your build into Rylais' Crystal Scepter. I usually begin with grabbing the Blasting Wand or if I have the money at the time getting the Giant's Belt. Once finished building into Rylai's you have a few options. You can either jump into Rabadon's Deathcap or you can start finishing your Hextech Gunblade. Most of the time I go into Gunblade because of the bonus Atk Dmg(Attack Damage). Most people ask me why i don't start into getting the bonus spell vamp. from here passive of gaining Atk Dmg, but I find that pushing out the bonus magic damage early is what could cause you to win or lose your lane. Now that may not always be true but in some cases it happens. Anyways after finishing your Raba's or Gunblade you now go into finishing Lich Bane. By this point if your killing left and right the game is generally over but in the event that is drags out after finishing Lich bane rap up with an Abyssal Scepter for the magic resist and more damage output. There is some other options such as Void Staff or some tankier items if need be.

I don't generally play Akali in ranked because people generally know how to counter her, but go ahead and try her out if you want to.