This is an Ashe build for a support/carry style.

With this build you should be able to not only slow enemies down so that others may beat them down but you will also be able to go 1v1 against most enemies by level 13, and come out on top 90% of the time.

Ashe, being a ranged support, is rather squishy but high in damage output. With a vast majority of skill points invested into offense you can get some serious DPS going by around level 8. Only 4 points go into defense, so that she can survive minor magic and physical damage. You will also be quite effective at minion farming so that you can purchase your items that much faster. A little bit of utility to ensure we don't run out of mana or health early game.

Mark of Desolation's so that you can shoot right through enemy armor like a hot knife through butter. Many tanks wont even be able to survive after you step into the frenzy.

Seal and Quint' of Alacrity to boost your attack speed and guarantee you get as many arrows out as possible. I find that by around level 10 you will be capable of delivering a constant barrage of armor piercing arrows fast enough to bring down even a Cho Gath or Rammus provided you have a buddy. At level 18 you can solo any body.

Glyph of Clarity will keep you nice and full of mana.

Sadly, in order to get the best of the armor penetration we have to sacrifice our Seals for physical attack runes.

Pretty simplistic in design. Hawk shot isn't going to be used often enough to warrant heavy investment so focus on Frost and Volley. Frost amplifies your Volley so that is why Frost gets the earliest attention. Also, Frost allows you to slow your enemies down repeatedly while you pick em off machine gun style.

Attack speed and damage all the way. And a bit of life steal too just in case.

The most bread and butter DPS purchase order known to mankind.

Ghost so that you can escape from sticky situations, or catch up to fleeing enemies so that you may deliver a rain of freeze and pain. Clairvoyance will maximize your scouting abilities, it also helps you know if you are being surrounded. For best results, cast it in the jungle above and behind yourself.

When starting a game purchase your items and follow your team mates. Use clairvoyance to see if the enemy is in position yet. Be sure to be BEHIND your team mates, otherwise the enemy will just simply slaughter you.

After the initial fighting is over get ready to farm minions and support your melee team mates by launching volley at your target followed by frost shot. This will keep them slow and vulnerable, plus you will deal a fair amount of damage.

Toggle off Frost Shot when you are shooting at minions. Keep farming for as long as you can so that you can buy items and increase your freezing power. If you can stay level with your enemies you should be extremely powerful by level 13 when frost shot and volley will be maxed out. At this time you should focus primarily on destroying the enemy players. Stick behind the front lines and focus on either the weakest or most healthy enemy. If you shoot at the weakest bad guy you will get a quick kill, but if you target the healthiest you will render him practically useless due to the constant freezing. Whichever works best in the situation.

At level 16-18 you can effectively crash towers solo. By this time you will already be an excellent tower diver so take the opportunity to do both if it is presented. Finally, if your team is having a standoff with the enemy right near a tower you can easily damage them from afar with volley. Hitting multiple opponents is your goal, when they are all frozen its a simple matter of letting your team rush in to crash the tower with brute force while you pick of and slow the enemy players.

Pros
At around level 13 you become a force to be feared
Your ability to rapid fire freezing arrows will lead to many kills and assists
You can kill any fleeing enemy with ease
Easy tower dive/crash
Excellent map awareness

Cons
Easy to kill in the early to mid game stage
Cannot jungle at all until late game, so no neutral buffs
You will be a primary target
You will need to manage your mana usage
Many accidental kill steals can/will occur, which may anger your team mates