[1/6/12] The Items page has been updated. You guys said you didn't like the icons and there wasn't enough reason behind it. I fixed it so go ahead and check it out. There's also a section in Items that tells you about how you should play in team fights. I may also put in a comments section. I've written some pretty important information in my replies and I feel like they should be included for those who don't read the comments.

Alrighty, maybe I'm a little full of myself or something but I have something to say. When I started playing Ashe, my first champion, I didn't know what to do. I built recommended and that was good enough for me. It wasn't until I hit level 5 or so that I knew what MOBAfire was, that's when I started picking up knowledge about the actual abilities and items through guides and builds. I used Your text to link here... <this build for the longest time after that and it worked alright. I followed it pretty much to a science and then I saved up enough IP for Irelia and I dropped Ashe and never looked back.
Now that I've gotten into ranked games, I've started to pick up Ashe again. I had the guide that I followed book marked and I went back to it to check it out. It really does need updated, yes, but I've found some other things that I just don't find helpful. This guide will pretty much be a modified version of that guide, however, almost everything is situational.

Now for the writing part. I'm going to make most of this very quickly and easy to read.
Armor pen marks: Honestly, every AD carry should have some kind of Armor Pen. The point of an AD carry is to get kills, and the #1 way to counter an AD carry is to build armor. It only makes sense to at least have a little armor pen so you can get kills on the tanky characters as well as the squishy ones.
Armor seals and Magic resist glyphs: Again, the easiest way to counter an AD carry's insane damage output is to have armor. AP carries need to be countered too, hence the MR. Obviously this isn't going to give you invulnerability. You're still pretty squishy, as you are with any AD carry. These runes are there to give you added defense earlier in the game, allowing you to be just a little bit more aggressive, which could really make a big difference getting kills early game.
Health quints: AGAIN, you are an AD carry. All AD carries are pretty squishy and it wouldn't hurt to have some extra health at the start. This combined with the health mastery will start you out with an extra 108 health at the start plus the mastery for health per level.

Masteries are pretty self explanatory. Take the masteries in Offense for attack damage, attack speed, life steal, and critical strike and give the other 9 to defense so you can get that extra armor, MR, and health. I shouldn't have to explain it more, because this is a pretty standard 21/9/0 tree.

ALL OF THESE ITEMS ARE SITUATIONAL.
I take either Doran's Blade or boots and pots to start. Take the first for extra damage for last hitting or the second option to stay in lane longer.
BF sword is after you get boots no matter what. I usually don't leave lane again until I have 1650 then I go back and get. You really do need that extra damage in order to harass the other team's carry out of farming and out of lane. The damage output also allows for more damage when your jungler comes to gank your lane.
I usually take Zeal next. The additional attack speed allows you to secure a kill if your jungler comes to gank and the other team starts t back off. You can really start to chase with this, although I would get a vampiric scepter or an Emblem of Valor for life steal. That way if you start to take too much damage but can't leave the tower, you can heal yourself off of the minion wave coming in.
NOW IS WHERE IT STARTS GETTING SITUATIONAL
I always finish out infinity edge before I start anything else, but if you don't have the gold, finish out blood thirster for damage. You really don't want to take life steal or attack speed without the damage to back it up, so at least finish one BF item before you go for things like stark's fervor and Phantom Dancer. Infinity Edge and Phantom Dancer are both great items to rush. They go well with Ashe's passive, giving her a higher chance to crit IF YOU NEED THE CRITS. If you are chasing down enemy champions at this point then I recommend going with those two. If you are team fighting at this point, your goal is to stay back and let the tank initiate UNLESS YOU FIRE YOUR ARROW. Regardless, your place is still at the back of the team fight picking off squishies. That's why Riot gave you range: to be able to deal tons of damage without being directly involved in the fight. Get your stark's Fervor to add to that BF item. If it's blood thirster just keep auto attacking and you will most likely survive the fights. Just remember that you are really squishy, despite runes, and that extra health. You're still an AD carry and you need to play like one.

YAY. This is my least favorite part, because I have to admit that I am wrong because so many people will debate with leveling up Hawkshot alongside Volley. I was one of those people too. Then I took an arrow to the knee and some sense to my brain.
You need to level Hawkshot first. The sooner you get that 5 extra gold from having 5 points in Hawkshot, the more gold you earn, the more items you can get faster, and you can even fire it into bushes that look guilty of holding Garens. It's really a wonderful thing, that extra gold. BUT PLEASE FOR THE LOVE OF GOD: HAWKSHOT DOES NOT DO DAMAGE. I don't know how many people I've said this to. They fire hawkshot straight into my face and I always type in all chat "[All] you know hawkshot does absolutely no damage, right?" They always respond "Yes it does." I always just lol and go on with letting them fire sparkles in my face. It's gotten to the point that it's irritating. STOP SHOOTING ME WITH HAWKSHOT.
Always drop at least one point in Frost shot so that when you shot Volley, it also slows.
Your Ult is great for stuns, but please, unless you're securing a kill or building AP, don't fire it for damage. It just doesn't do enough to damage anyone. It maxes out at 3.5 second stun though so if you see a team fight about to errupt and you're back at base, don't be afraid to shoot that arrow into the enemy team. Again, at max range, the arrow stuns for 3.5 seconds. In League time, that's somewhere between the beginning of time and the end of the world.

I think all ranged AD carries should take exhaust. Ignite is dandy and all but if they are about to run, drop exhaust and right click. It really is what ranged AD carries are meant to do. Right click 'til they die.

EVERYTHING IS SITUATIONAL/OPTIONAL. DON'T TAKE IT AS ME TRYING TO CREATE THE BEST ASHE GUIDE OUT THERE.

This is the way I play her and I think that it would help some of the people who are struggling to get out of ELO hell. Just carry yourself out with a ranged AD and you'll be good to go.

I mean
It's Ashe
It can't really get much simpler.

Comments and criticism are welcome. If you have anything you'd like me to add then sure, unless I think you're wrong. :P