Pros / Cons

Pros
+ // Has a slowing ability (Make it Rain)
+ // Great damage
+ // Great Harassing and farming abilities

Cons
- // Pretty squishy
- // Usually targeted in team fights (As all AD-carries are..)
- // Needs to be positioned well

Strut
//Miss Fortune gains an additional 25 movement speed after not taking any damage for 7 seconds.
// This is a pretty cool passive to have. If you run around your lane it might be hard for the enemy to use skillshots, but that's just about it. It makes her fast. That's all there is to it.

Double Up
//Miss Fortune fires a shot at an enemy target, dealing physical damage and 115% of that damage to another enemy target behind the first.
// I think this one of the best harrasing abilities in the game. It's pretty straight-foward on how to use it. You could either hit an enemy champion directly, or hit a minion if you're sure that it will bounce to the champion.

Impure Shots
// Miss Fortune's attack speed is increased for 6 seconds
// This can be pretty usefull if gonna fight a champ head on. Other than the active it also has a passive where miss fortine's autoattacks deal extra magic damage on-hit, which can be really cool.

Make it Rain
//: Miss Fortune fires hundreds of bullets into the air which rain down at a location.
// I think this is my favorite Miss Fortune ability. Other than the damage it also slows enemies and reveals the area it's cast on. Which means you can check the brush for enemies.
Yup. No more facechecking for your team.


Bullet Time
//Miss Fortune channels for 2 seconds to fire a wave of bullets in a cone in front of her every quarter of a second.
// While this is awesome ultimate it's really hard to use.
You need to position it well and you also need to keep in mind that it can be avoided pretty easily. It would be ideal if Sejuani would jump in stun all the enemies and you just blast away. But nah, that's probablly not gonna happen :x
In any case, if you can't stun them to keep them in place for your ult you might as well slow them with Make it Rain.

Early Game

So early game as you can see by the given build and skill sequence you want to start off more on the AD side. Miss Fortune can pretty much lane anywhere, but I think it's best to go bottom with a support. So, head over to your lane right after purchasing Doran's Blade or Boots of Speed.

She is a ranged champion and you can easily shot at enemies when they're paying attention to others. This is a great place to use Bullet Time and Make it Rain.
Specificly, use Make it Rain just a tiny bit behind them and then use Bullet Time.
Why? They will be Slowed by Make it Rain, and this is why they can't easily avoid Bullet Time. Use Double Up when enemy champions are weak, because of the strength of it, and because there is a chance you will hit another enemy champion. As for Impure Shots you can use it when attacking an enemy head-on.
Otherwise stay close to your support, and look for good targets, and good moments for Bullet Time.