(UPDATED) READ THIS: Core of this guide was made when I wasn't experienced player, but I refused to delete it because its so cute ^.^ I decided to spice it up with some troll-builds (they aren't worthless, but it would be insane to go ranked with one of them). Good luck, summoner :)
1. Guide is supposed to be serious guide. Quite old but it still works with some farm :)
2. "Bloodbound" build with alot of lifesteal. Really funny when your BT's get fully-stacked.
3. Tired of being insta-killed. Here comes the Badass Bruiser MF :D
4. Also, if you are thinking about her AP ratios, try this build. Positioning + Ultimate = Not Bad.
Welcome to the Learning center about Miss Sarah Fortune, The Bounty Hunter. Many people thinks, that champions like Miss Fortune dont need guides, but there is big difference between novice MF Player and skilled one. This "Easy difficulty" on champion's Info says how much is champion hard to learn, NOT how much is he hard to master. Also keep on mind, you can be even the best carry on the Fields of Justice, but without synergy with the rest of the team, you are useless (except against Bot/Noob match). It toke me much time to make this build serious, I hope you will appreciate it. Through reading my guide, you can experience some unanwsered question, feel free to ask me. So where to start?.. oh.. uhm.. SET SAIL!

PROS
+ Your Attack Damage is like from another world.
+ Also has big Critical and not-bad Attack Speed (your W can ever improve it)
+ Lifesteal ensure you some survivability (some kind of 1000 HP regen per 5 sec)
+ Item build isnt much expensive (for MF's ability to farm its like nothing)
+ She is tough early game [If you have some Golds to stack some Doran Blades (more about it later)]

CONS
+ She havent any resists or tons of Health, when she gets heavy CC-ed, she is dead
+ Need smart tactics to never become easy target
+ Also must play carefully due to your Stack-Up Items, when you have chance to kill somebody, but you are on 100% sure you will be killed too, dont do it...

My runes are not big surprise, I am using:

Greater quintessence of desolation 3x Quintessence of Desolation (+ Armor Penetration)
Greater mark of desolation9x Mark of Desolation (+ Armor Penetration)
9x Seal of Fortitude (+ flat Health)
9x Glyph of Celerity (+ per level Cooldown Reduction)

Overall, i have pretty good Armor penetration (when Black Cleaver is bought, i have enough pen to make some hurt), some Health (early game I can stay a bit longer on lane, result is more Exps and Golds) and Cooldown Reduction that is big + for my Buller Time

Summoner spells, you can choose by yourself, everyone prefers something other, I prefer Exhaust and Flash.
UPDATED: HEAL SEASON! :)
UPDATED: I still think, that picture is right, even if some spells are out and some are in, ignore Rally and Fortify, Promote take as "NO WAYY!" and Surge as "Can be too..."

I have nothing to say about this. You can see it on most of DPS guides. 21/0/9 is evergreen for Carry like you.

UPDATED: Now when masteries are completely different, I still think 21/0/9 is most viable on any ranged carry like you. It dont need any deeper commentary...

My items arent surprise but its very effective combo, that include all offensive properities: Amazing Attack Damage (2,3,4,5), Huge Critical (5,6), Nice attack speed (1,4,6), Lifesteal (3) and Armor Penetration (4)

Yes, they arent for newbies due to 2 stackable items and zero survivability. IF YOU ARENT SKILLED MISS FORTUNE, SKIP BUILDING SWORD OF THE OCCULT AND JUST BUY FROZEN MALLET (when your team lacks constant slower) OR IN THE OTHER CASE GUARDIAN ANGEL.

Why you stack Attack damage instead of more Phantom dancers? Anwser is simple, you got W, and you have epic AD ratio on your ultimate.

I think, Main Core are first 5 items, Im buying Phantom Dancer in 75% cases. other good choices are:
1. BANSHEE'S VEIL: Yes, you though i forgot about this but now way... this Item is excellent on Miss Fortune when enemies are clever and always ready to interrupt your Ultimate frenzy, in this case, i choose Banshee. Im building it before Infinity Edge.
2. GUARDIAN ANGEL: Another surprise for your foes. When you are at match, that is about nothing other than Team Fights and your team dont have any Tank, this is good thing.
3. FROZEN MALLET: Hmm, i dont like it on Miss Fortune, I buy it when my team sucks and cant cooperate and I must catch bad guys without help of supports, so I need more slow than from E ability. As I said i dont like it, if Im playing Premade, im always with guys that can help me with chasing. (in my opinion, best support for MF is Singed)

UPDATED: Its matter-of-course thing, against Heavy armored team buy instead of your Black Cleaver...

STRUT: This ability allows Miss Fortune to be Miss Fortune. It reveals her many possibilities.
1. Wanna Gank? No Problem.
2. Wanna Quickly push another lane? No Problem.
3. Wanna fly across the map to farm a huge creep horde? No Problem.
Also gives you sense "I must stay unharmed". Really awesome thing.
.
DOUBLE UP: Hello bad guy, wanna farm? DENIED! Use to harras, harras and harras. Never use on creep last-hits (until you have Golem/blue buff), This ability needs some practise to calculate, when bullet can bounce to Player, and when not. NEVER harras enemy by targeting him instead on creep (only when ganking or when there arent any creeps) Always keep on mind, that ability can have Awe-some range (up to 1125 when you are real sharpshooter). You can exploit it when you chase an enemy with a bit of Health on his lane and when his creeps are arriving, lock last minion to bounce it and takedown him like a pro.
.
IMPURE SHOTS: There's not much tricks hidden in this ability, maybe only, when in Team Fight, and your Ultimate is done, divide Impure shots between ALL enemies, after that you can focus on one guy. Whenever you will meet guys like Mundo/Vladimir/Warwick/Nasus/some Healer or anybody with stacked Bloodthirsters, use your Impures as much as possible, this will ruin them...
.
MAKE IT RAIN: Farming tool? Forget about it, this ability has better use.
1. Slow enemy while chasing him
2. Slow enemy/enemies while fleeing
3. Exploring brush
4. Combine with your Ulti (more about it later)
.
BULLET TIME: this ability have its own Chapter called "Its Time for the Bullet Time" because it is too epic to leave it in "Abilities" chapter. ;))

About skill sequence: its not much important thing, only always make 1 rank on "Make it Rain" at start of match and Rank-up it as last one,

Yeah, its Time, finally... It is one of my Top 3 reasons why I play Miss Fortune:
1. BULLET TIME
2. Her Crazy Laugh
3. I like pirate scheme

Maybe the most tricky thing on Miss Fortune (especially when you are facing Pro team), It is channeled ability (you can be interrupted easily), it needs choose right angle/distance, and know when it is good choice to release it. When you release ulti alone, combine it with your E ability, in Team Fights, dont waste time with E, only quickly release R, when its perfect time. Perfect time... when it is? There are several ways to make your YEHAHAHAHAH-time perfect. When you have in team champion like Amumu, Galio or Nunu, only wait when they will start their ultimate AoE madness. When have Morgana, collude with her to drop her shield on you and then let her use her Soul Shackle. You will become immune to Crowd Control (perfect while channeling), and enemies will be slowed by her ulti. In other cases, base your Ultimate on Surprise and perfect Timing. This need Practise...

Doran Blade, perfect starting Item for Miss Fortune, gives you all you need on comfortable laning early game.
+100Health : total Health on lvl 1: 668, its good number for ranged carry. (Damn nerf, now its only +80)
+10 Attack Damage: total Damage on lvl 1: around 65, with 31 armor penetration from runes/mastery... I dont have words...
+3% Lifesteal: its like a +5-8 HP regen per 5 sec if you constantly attacking something. Its more decorative than effective thing, but why not?

When you are alone lane, or on Top/Bot lane but your laning partner isnt much active at farming, You can farm Great bounty by last-hitting method "I always shoot first.. ow not, I always shot last ;)". With Wealth you can afford (after buying Shoes) ONE MORE or even TWO MORE Doran Blades. It can lead to multiply your outcome from farming and also making you extremly durable during Laning phase. You will be dominating in lane.

You can notice, I have nothing on Mana/Mana Regen, someone can say "but.. but... but you need mana!". Yes, mana is important for every champion (except manaless champions of course), you only must know how to spare that little blue bar.

Early game its worst, you can easily waste your mana pool in 10 seconds and then wait 4 minutes to fully recharge, if you dont want recall back. If theres isnt Jungler in your team, try get Golem buff as often as it possible to give Miss Fortune freedom with casting.
DOUBLE UP: costs 70/75/80/85/90 : this is not cheap ability it can eat big amount of your pool, use only when you have nice opportunity to harras enemy hiding behind minions. Make at least 15 second pause after use it. when ranks go up, you can decrease your pause into 10 seconds, when on Blue buff, do it as much as you can. NEVER use Double Up on minions early game.
IMPURE SHOTS: costs 50: this ability dont need any sparing, costs 50 mana at all ranks, and has big cooldown. If you have enough mana, use to farm more quickly. When someone is trying to Heal over time (perfect example is Dr. Mundo), feel free to cripple his Sadism lust with it. When pushing, ALWAYS activate it.
MAKE IT RAIN: costs 80/85/90/95/100 : watch out! this is your most hungry non-ultimate ability. Fortunately, my build says "keep it on Rank-1 until you get lvl 14". This ability will become more useful in later phase of game. NEVER use to farm early game.
BULLET TIME: costs 150 : Priority number one, always keep at least 150 mana in your "bag" for your dear ulti. You CAN farm minions, if they are stacked at your turret, If you want to leave lane to recall and you still have some mana, use on any group of minions to farm 200-300g in 2 seconds.

There are several Anti-Fortune guys, you probably know them, but lets revise it:
..
These guys arent much dangerous, they usually have lower HP bar than you BUT, they can blind you and make your Physical Attacks do nothing. Always try dodge Heimerdinger's Grenades, and when Teemo hits you, (cant be dodged, except you have banshee or something like Black Shield) harras him with your Q and E.
..
These are more dangerous than previous ones, these (and many many more) can completly disable your actions. First two (ALL guys with silence or/and Knock-up) are dangerous only while in Team Fight and you want to release your cone of death, other three (ALL guys with Stun/Fear/Taunt) are lethal all time, because when you get Heavy-CC-ed among enemy Nukers, you are vulnerable to die.

Just must-know things, before you get on the fields of justice.

- Never initiate (ofc).
- If you have heavy AoE battlefield controller in team (Amumu, Galio,..) Wait with your own ulti on right moment.
- Mid-late game, use your E to check brushes, will save your *** in many situations.
- If your enemy team got SWAIN, MUNDO or VLADIMIR, save your W until they appear (in larger teamfights, not in 1v1).
- Farm as much as you can, ask for your lane partner if he cant let you all the creeps.
- Use your Q right after autoattack, especially early-game.
- Dont be too confident, you can get nuked easily.
- Dont forget to deal TONS OF DAMAGE!

I Hope, my build helped you someway. I am sorry about my grammar, Im not native speaker..

UPDATES:
2011-05-05 : Added MODE called "BloodBound", for fun ofc, here is real Stats LEAGUECRAFT
2012-01-19 : Updated on SEJUANI Patch, Added MODE called "U mad MF offtank?", not serious build, but i had some funny moments with that ;)
2012-06-29 : Cleaning! Guide got some good reactions so I decided to fix several things here. Also added another Troll-build (AP)

Statistics on this site arent 100% accurate and doesnt count some things. Here is more detailed Stats: LEAGUECRAFT

Thanks to:
of course http://www.mobafire.com
http://leagueoflegends.wikia.com
http://leaguecraft.com/champions
http://imageshack.us
http://translate.google.com
Windows Paint (lololol)
Mozilla Firefox
Ponies
Everybody, who leave me +Rating