Introduction:

This is the build I pretty much use every single time I use Miss Fortune. She's my best character, and I rarely do badly with her. This build will support you from the beginning of the game up until the very end ... and support you very nicely.

Strategy:

Health

Miss Fortune is quite a relatively squishy character, so you have to be careful when you play with her. Miss Fortune is commonly found in mid, so a gank from either side is quite possible. Therefore, when you are in mid, alone, be careful. Watch the map very carefully to determine if any opponents have gone missing, and if they have, (or if your teammates "mia") run back to the tower. Especially early game, Miss Fortune cannot survive a well-planned 2 v 1 gank.
If you go to either top or bottom, your teammate can help you take the damage, especially if he or she is a melee character. Since you are a ranged character, take full advantage of that and stay as far away from the battlefield as possible while sniping (last hitting) minions.

Passive

Miss Fortune's passive is quite an interesting one, as it can be both a very, very big help or a huge hinder. Her passive is, after 7 seconds of not being hit, that her movement speed is increased by 25, and increases by increments of 4 to a maximum of 70 bonus movement speed. This, as I said, can greatly help you when you are running from one side of the map to the other. However, if you are trying to run away from a gank, and you lose your passive, your movement speed is greatly diminished and are you are quite vulnerable to dying.

Farming

Because of my inherent attack speed, I always end a game with the most minion kills. Well, not *always*, but more often than not. This can help you drastically when you're desperate for money, because having this great attack speed will get you money. Use your "Make it Rain" spell to help your farming attempts.

Team Battles

Because of Miss Fortune's lack of health, she can be quite difficult to handle during big team battles. You can solve this by doing several things. First of all, you can hang back, away from any direct fighting and snipe your opponents while your teammates take the damage for you. However, this does not always work, as on occasion the enemy does not always do what it should do, and they sometimes will come after you. If this were to happen, you should run. Just run. A second solution, one which I prefer more over the above, would be to have enormous amounts of lifesteal. With two bloodthirsters, you would have enough lifesteal to stay a viable source of damage during a team battle.

1 v 1

Miss Fortune is a meritorious solo battler. If you are not afraid of being ganked, I would almost always engage in a 1 v 1 battle. I very rarely lose in 1 v 1 battles, especially if my item build is complete. However, a word of warning. If your opponent has a stun, this could be quite bad for you. If you cannot keep attacking your opponent and utilizing your lifesteal, you're in trouble. Therefore, if you are going up against someone with a stun, watch out. Advance only at your own risk.

Items:

As for the items, you first buy the Doran's blade. After that, the Berserker's Boots. The next few items are the Sword of the Divine, Phantom Dancer, Black Cleaver, and Blood Thirster. After that, sell the Doran's Blade, buy the Infinity Edge. After the Infinity Edge, sell the Sword of the Divine and buy the second Blood Thirster. After that, sell the Beserker's Boots and buy the final item, the Madred's blade, but only if necessary. If the other team has a lot of strong, tough, hard characters, I would recommend buying the Madred's earlier on, maybe around the time you would have bought the Black Cleaver. But if their entire team is composed of squishy characters, I would recommend an item like Trinity Force. If you are having trouble chasing them down, get a Frozen Mallet.

This item build will give you a 2.4 odd attack speed, and 400+ damage, and that does not include crit. strike, which should be around 60%. I have found that even 4,500 hp Alistars with 250 armor last about 2 - 3 seconds under my full firepower.

This build is very effective in both 1 v 1 battles and team battles. This build will effectively combat tanks, mages, and other dps heros. Unless they gank you all at once, you should be fairly well off with two bloodthirsters keeping your lifesteal fairly high. I have gone in 3 v 1 before and won :).

Spells:

As for the spells, I level up "Make it rain" as soon as possible because it is an excellent farming tool. In addition to this, you can effectively use it to either escape or chase down opponents. I don't find much use for "Double Up," because when you're attacking at the speeds at which you will find yourself if you use this build, double up is not worth the time it takes to set it off. Impure shots is a mixed blessing and curse. It is a blessing, for sure, in the beginning of the game when you don't have your full item build yet. However, towards the end of the game, it becomes a wasted skill, because you will be very close (if not already there) to maxing out your attack speed. However, its passive is quite nice ... especially during the earlier phases of the game.

Masteries:

My masteries are quite simple. I have maxed out all the useful attack masteries, such as Havoc, Lethality, Burning embers, etc. These should give you a small edge when it comes to attack speed, damage, and ap. The leftover masteries go towards Good hands, meaning you're going to be dead for a lesser amount of time. *NOTE* Edit: It has been brought to my attention that using Archaic Knowledge is a better option. Therefore, I have modified my build to conform to such opinions.**

Runes

As you might have noticed, every single one of my runes points towards attack speed. I am an attack speed fanatic. I love, love, love attack speed. These runes, when all added up together, roughly equal one attack speed item. My reasoning is that this would allow me to buy one less attack speed item and one more attack damage item (Infinity edge). This greatly increases Miss Fortune's damage output.

Summoner Spells

My summoner spell layout is quite simple. Because Miss Fortune is quite squishy, and therefore liable to die in ganks, I use flash. Flash enables me to escape from situations I would not have otherwise been able to escape. It also can be used offensively, to chase down an opponent (while used in conjunction with Make it Rain).

Ignite is also a spell which I very fond of. In the early game, I love the ability to just whittle someone's health down, and then just put ignite on them and watch them die ... all from a safe distance away from the tower. Without ignite, they would have just run to safety. Ignite also has a place in the later game, because it limits people's ability to escape, even when towers are not in the picture.

End Result

Miss Fortune is one of the most fun characters with whom to play - at least for me. Her versatility to be able to effectively participate in team battles and solo battles -- not to mention that it does not matter to a large degree who she faces ... tanks, mages, or other dps heros ... -- makes her able to face almost anyone in the game and win, if in the right hands. She, time and time again, has proven her quality as one of the best DPS heros in the game.