This guide is mostly for me right now, as I am trying to use Ashe to get me out of ELO Hell at the moment.

Pros:
-Very high damage late game, even if your team is losing you can carry everyone out!
-You can refill your HP in just a few hits on minions
-You are a tank destroyer
-You are an everything destroyer!!!

Cons:
-Thornmail hurts like a mofo
-You are squishy so you have to play it safe
-Final build requires ALOT of gold

-You could Solo top because you have teleport, but if its not 1v1 up top other champs are better for this role.
-Solo Mid is a great place for Ashe as its easier to last hit, but people always will try to gank you
-Bottom is fun if you have a great lane partner, otherwise getting last hits can be a pain
-Do not jungle with ashe until mid to late game, you need that gold!

--Notes on Jungle--
As you are walking to your lane (TP on CD or your saving it) be sure to pick up golems, wolves, or wraiths on your way to your turret. The extra gold helps in the long run

This part gets it own section because Ashe gets ganked ALOT when she pushes towers. Do NOT push tower unless your Hawkeye is avilable so you can see if people are coming up behind you. Or just buy a ward to be safe.

NEVER PUSH TOWER unless you can see behind you! The more you die the more its harder for you to keep your gold up for this build.

Early Game:
-Last hit as much as possible
-Dont go back to base unless you are out of potions and your HP is BELOW 30%
-Teleport back so you dont miss out on XP
-Dont push tower unless you can watch your back
-Last hit as much as possible

Mid Game:
-Mid game is when your around lvl 11-14
-At mid game you should have all items above up to Zeal for phantom dancer, i like to call it the all yellow point because all your items are yellow.
-You will use your teleport mostly to help others at this point, they are taking top? tele top, 2v1 bot? tele bot to help
-At this point you will do pretty decent damage, so you will start to become a main target

Late Game:
-You can now destroy tanks, you will do the most damage to them even without armor pen
-You can focus anyone and take them down
-You are the main target for their team, they will always go after you so stay very far back
-DO NOT start battles, just end them
-Teleport to where you are needed
-Hawkeye often to chace
-Blue and red buff are very very nice at this point

Hawkeye is your second skill, to help you gain gold on your last hits and to also keep an eye out for bushesh. When chasing a champ, be sure to shoot hawkeye ahead of them so if they enter a bush you can still attack/slow.

Hawkeye is your best friend, its a moveable ward with a very short cooldown, plus it helps you out alot from being ganked.