Hello everyone! This is my first guide here on Mobafire. I've been playing Akali for a few weeks now and I thought that I would share my secrets to my relative success with the whole LoL community so that we all can become better Akali players! Here I go!

Akali is an AP melee champion; one of the few in the game. That being said, she is an amazing (anti)carry, with emphasis on killing weaker champions being her purpose. Her burst is insane, and with mastery of Twilight Shroud, Mark of the Assassin and Shadow Dance, virtually unavoidable. This guide will help you achieve incredible levels of success with Akali, all the while having a great time!

Pros
Filthy burst
Sustained damage is decent (if you pace your ultimate and your q's out)
Insane 1v1 capabilities (WILL destroy squishy champions unless you play LoL with only 1 finger...)
Farms well
Agressive in Lane
JUKE!!!
Incredible chasing ability

Cons
Squishy
Needs both passives to be strong in early game
Can be countered easily (Beefy/stuns/Oracles)
Requires moderate skill to perform well

Twin Disciplines
Akali's passive; perhaps the MOST vital skill she has. She gains 10% spell vamp from her first 10 bonus AD, with an increase of 1% spell vamp for every 5 AD thereafter, and she gains 10% bonus magic damage added to her auto attacks for the first 20 bonus AP she acquires, increasing by 1% for every 5 AP thereafter. With runes and masteries, both will be active by level 2, which is when you should start harassing.
Protip: Do not try to build Akali as AD; while her spells may heal for a fair amount of their damage; the lack of AP will make Akali's spells hurt as much as wet noodles. Akali has phenomenal AP ratios, so I focus on building almost purely AP.

Mark of the Assassin
Akali's Q, and her main source of damage. Akali throws her kama at an enemy, marking them for 6 seconds. If she autoattacks the marked target before the debuff expires, the mark detonates, doubling the damage of the spell. This spell works well for last hitting creeps early game well above 100 hp. You can use it as a ranged last hit too, if you time it right. When using Mark of the Assassin to initiate, wait at least half a second before using Shadow Dance, otherwise her first autoattack will NOT trigger the mark, thus wasting an AA. If you do Q, wait .5 sec, R, Q, you can detonate 2 marks in under a second, which is where Akali's incredible burst comes from. Also, detonating marks refreshes energy, which helps while farming/teamfighting.

Twilight Shroud
Akali's W, her defensive move. Twilight Shroud places a stealth zone at the target location which lasts for 8 seconds. While in the shroud, Akali is invisible and gains armor and MR. Autoattacks and spells cast while in the shroud will briefly reveal Akali. Twilight Shroud also slows all enemy units that walk through it. This spell is useful throughout the entire game, from level 2 harassment to level 18 teamfights. Twilight Shroud lets you decrease incoming damage, close the gap on fleeing prey, gain distance from champions chasing you, avoid targeted spells/stuns, juke and farm. Twilight Shroud is very useful, but it will be most helpful if you use it correctly. If you feel that a fight is lost and you want to flee, save Twilight Shroud for after they've blown flash/ghost or have their moves on CD. If you blow your shroud and get caught, you will be ravaged in a second. Akali is squishy, but you will rarely die if you master the use of Twilight Shroud. Know when to not use it too; as it costs a lot of energy early game.

Crescent Slash
Akali's E, and her farming/throwaway ability. Crescent Slash does ****ty damage compared to Mark of the Assassin, but it is AoE, so it is used 99% of the time for farming. ONLY use Crescent Slash in a teamfight if your Q is on CD and if you have no stacks of Essence of Shadow to use your ultimate. That being said, Crescent Slash is a fine ability, just prioritize your Q in fights.

Shadow Dance
Akali's Ultimate; initiator/ranged execute/juke/combo/finisher... Words cannot describe what Shadow Dance can do, but I will give it my best shot. Shadow Dance is on a 2 second CD and costs no energy, but requires an Essence of Shadow to use. Akali can stack up to 3 Essences, which take a fair amount of time to accumulate. However, Akali does recover an Essence of Shadow on kills and on assists. In a well executed teamfight, Akali can get a Quadrakill or a Pentakill and run away with 3 Essences of Shadow. Mastery of this spell will save you where Twilight Shroud cannot. Using Shadow Dance with or without Twilight Shroud to juke enemies can get Akali out of the worst situations unscathed. Usually, Shadow Dance will be used in combination with Mark of the Assassin to perform burst damage on the enemy team's carries and shred them to pieces. You can use an Essence of Shadow to dash to a creep to get in range of an enemy champion as well. Akali can not Shadow Dance to allied units (sorry, no leap strike/shunpo to a ward) but, in the jungle, warding camps will allow Akali to see and Dance to neutral monsters through walls. Shadow Dance is truly an ultimate ability.

Ignite
Ignite is an excellent choice on Akali. Ignite often helps secure first blood on many champions, but with Improved Ignite, using it as an initiator at level 1 will activate Akali's AP passive (which my build doesn't activate until level 2). Many people claim that Ignite loses its effectiveness towards late and end game, but at level 18, Ignite does a total of 410 true damage, which is often 20ish% of a carry's health at level 18. Obviously, it also helps kill champions that rely on regen alot (Mundo, Vlad, Swain, Nasus)

Flash
Flash is an amazing summoner spell on every champion. Flash allows you to create/escape ganks, jump over walls, dodge long stuns/skillshots, and with Akali, exit Twilight Shroud suddenly for a clean getaway.

My rune setup focuses on activating both halves of Akali's passive by level 2 (In conjunction with masteries) without sacrificing late game damage and survivability. The 2 Greater Mark of Magic Penetration help Akali's spells hit just a little harder. The 7 Greater Mark of Attack Damage help activate the AD portion of her passive. The 9 Greater Seal of Vitality give Akali just a little more health (170 actually). The 3 Greater Glyph of Ability Power, along with the 3 Greater Quintessence of Ability Power help activate the AP portion of her passive. The 6 Greater Glyph of Scaling Ability Power giver her slightly more AP than Greater Glyph of Ability Power by mid/late game, but if you prefer straight up Potency Glyphs, then go for it. You may also opt to go with full Greater Mark of Magic Penetration, but you will be forced to start with a Doran's Blade to get the other half of your passive active, sacrificing sustainability in the process; Doran's Blade does give health and lifesteal, but I don't think its worth it (Boots+3 Hpots > Doran's Blade). The Seals are entirely personal preference; you can grab the +Energy seals if you prefer, but a well played Akali will never run out of energy, especially with blue buff.

Offense
Row 1:
Deadliness 3/3: You need at least 1 point here to advance in the tree (I don't use Exhaust/Smite on Akali) and the 2 extra points are better spent here than anywhere else in the tree.
Archmage's Savvy 3/3: More AP/level is perfect for Akali, and this mastery helps activate the AP portion of Twin Disciplines by level 2, which is key.
Row 2:
Sorcery 4/4: Needed for Archaic Knowledge
Row 3:
Burning Embers 1/1: Ignite is a staple summoner spell on Akali; a lower cooldown and bonus AP while it is on CD is icing on the cake.
Archaic Knowledge 1/1: Gives your spells and the bonus magic damage on your autoattacks the ability to hit harder and do more damage.
Sunder 3/3: Penetrating armor with her autoattacks helps her last hit and harass.
Offensive Mastery 2/2: Helps farm.
Row 4:
Brute Force 3/3: Needed to advance in the tree and needed to activate AD portion of Akali's passive.
Row 6:
Havoc 1/1: You're this far already and 4% increase to all damage is nothing to sneeze at, especially when you can burst a carry down in 1 combo.

Utility
Row 1:
Good Hands 3/3: EVERYONE hates dying in this game, and the less time you spent dead, the more time you spend alive and killing enemies.
Perseverence 1/3: Only half useful to Akali (she doesn't use mana and thus doesn't have increased mana regen) but is needed to advance in the tree and is more useful than improved Heal or Ghost.
Row 2:
Awareness 4/4:
Perhaps the best mastery in the game; more xp=faster leveling, which helps you do everything.
Row 3:
Utility Mastery 1/2: Better than everything else available; helps extend blue buff, which is something you should grab every time it’s available.

Start
Start with Boots and 3 health pots, regardless of which lane you're heading to. If you're new to Akali or lack the proper runes, grab a Doran's Blade to give you HP and activate your passive if its not activated.

First Recall
Don't come back until you have over 1200 gold, unless you just killed an enemy and have some time to get back to lane. Grab Hextech Revolver, which i believe helps tremendously in the laning phase, a Health Potion (if you think you need it/are being dominated in lane) and some wards.

Boots
Boots on Akali are personal preference, between Mercury's Treads and Sorcerer's Shoes. I personally go for Merc's because I believe Akali does enough damage without the +20 spell penetration from Sorcerer's, and because I believe that Merc's have a more to offer.

From here, I decide between Lich Bane and Rylai's Crystal Scepter. I get both in 100% of my games, but knowing which one to get first depends on the game. If you're having trouble chasing enemies/need more hp, then grab a Giant's Belt and build into Rylai's. If you are having an easy time farming and know you can win your lane easy, buy a Sheen and build straight into Lich Bane. I believe that both of these items, along with Hextech Revolver, make up the core of Akali's build. Personally, I almost always build Lich Bane first, as I have no problem chasing down enemies until they build health and defense, which often doesn't occur in early/mind game.

If you are doing well, go ahead and rush Rabadon's Deathcap after BOTH Rylai's Crystal Scepter and Lich Bane, building it through Needlessly Large Rod.

From here, I almost always build a Void Staff and then finish off with Hextech Gunblade, however, if I'm being focused, I'll drop my Void Staff and build a Guardian Angel or a Banshee's Veil. Buy Zhonya's Hourglass if you are getting focused often; it helps tremendously. Quicksilver Sash is necessary for teams with a Warwick, a Malzahar or a champion with a blind or powerful/multiple DoT/snares, like Teemo or Swain.

At the end of game, get all 3 consumable potions (and an Oracle's if they have a stealth carry). The potions give you HP, AD, AP, AS, and Crit, all of which are useful; don't undervalue the consumables!

Akali's item sequence is fairly limited; building defense is a waste because you shouldn't really be taking damage, and the offensive items she uses are undisputable. If you don't feel that you need the spell vamp from Hextech Revolver, you can drop it, but I highly recommend it, even for experienced Akali players. I recognize that this build is expensive, but if you follow my guide, you will be able to amass the gold to build these items, assuming you can farm.

I start out with Mark of the Assassin for harassing, farming and the occasional level 1 first blood. I max this spell first because it is Akali's main source of damage.

I put a point in Twilight Shroud at level 2 for harassing and protection. I max it last because each new level only drops the energy cost and barely increases the bonus Armor and MR. The slow is also negligable; rank 1 is all you need to get away and kill people.

I put a point in Crescent Slash at level 4 and for farming. I max it second because it helps me farm and once in a blue moon it gets me a kill (only when Mark of the Assassin is on cooldown!!)

I level up Shadow Dance whenever I can, for obvious reasons.

Akali's role in Team Fights is to kill the enemy carries. Akali's abilities are designed around getting around the tanks, protecting yourself from targeting, and attacking with huge bursts of damage on your terms. Do not initiate as Akali unless you are supremely confident that your team has your back, or it is not a full teamfight and you know you can avoid most of the damage. Remember, it does not matter how amazingly hard you hit if you die before you can do any damage; a dead player is only useful to the other team.

As of 7/27/2011, I have not played Akali in ranked matches, however I know that she is perfectly viable. If you are interested in watching good Akali players, watch Westrice's stream whenever he plays; I learned to play Akali from watching him. Akali is best picked 4th or 5th on your team. Akali is easily counterable with tanky/dps champions and stunners, so wait to pick her and ONLY pick her if their team won't prove to be too much of a problem. This build focuses on success as a carry and an anti-carry in both normal and ranked games.

Akali is an incredibly fun champion that requires moderate skill and is extremely rewarding to play. Remember, my guide is not the Akali bible; it is simply how I play her and I am sharing it with the League of Legends community because I believe that my playstyle is viable. Try my guide before commenting or voting (Akali EXCELS at killing trolls) and feel free to offer any constructive criticism; I am far from being an incredible Akali player.