THIS IS THE BUILD I USE TO DO WELL WITH TALON! THIS IS NOT PERFECT, OR EVEN CLOSE, BUT I GIVE YOU MY BEST!
If you like the build, please rate it up, or just use it to kill me when you're playing me. :)

On the top, it says Talon's health will be 700. This is not correct. They have not put in the base stats for Talon at level 18, so his health will be higher than 700, along with other stats of his.
Please look at the actual guide on the bottom before uprating/downrating. It will provide an explanation of why I get the items I do in that order.
I have 2 builds up for Talon. There is not much difference, except that the item order has been moved around a little bit, and the 2nd one shows the extra Phantom Dancer at the end. I encourage you to try both and see which one you like! :)

Good:

Can kill people instantly
OPed late game
Super fast at taking out turrets/inhibitors
Able to escape ganks
Good ganker (with his stealth move)

Not So Good:

Early game is tough
Targeted first in team fights
Has to farm well to get OPed
Killed VERY fast if CCed

First off, I picked the Greater Mark of Alacrity Runes because it gives you quite a bit of attack speed to begin with. It's a lot easier to get those last hits on minions in the beginning when your hitting faster. Next, I chose the Greater Seal of Attack Damage Runes because it gives you a little bit more OOMPH when your last hitting, or even hiding in the bushes to jump on a guy at the beginning. Then you got your Greater Glyph of Armor, mostly so you don't die to those Level 1 ganks in the bushes early on. Last but not least, you get the Greater Quintessence of Attack Speed, which will increase your attack speed by a whopping 10%! That's really helpful when you are trying to backdoor or just take out a turret.

For other possibilities, I also like the Greater Quintessence of Desolation Runes to take out those pesky tanks late game.

For the Masteries, I went with a basic 21/0/9 build. You're an assassin, so you'll want to do as much damage as possible, which is why you have 21 in offence. Then you've got the 9 in Utility to help with the little things, such as time spent dead or an extra gold per 10 seconds. Those actually are very handy, and can serve you well late game (not the gold, but the time spent dead ;)).

I go with Flash and Exhaust for my spells. I use flash because it is very useful for getting in or out of ganks, and it will save your life plenty of times. Also, Exhaust can be used to get away or initiate a fight. I find this spell very useful when facing a Xin Zhao or Master Yi (if he's not using Highlander)

Other descent options would be to use:
: Good use for finishing someone off, but when you have Noxian Diplomacy, there is no need for Ignite.

: Great for staying in lanes early and getting all that extra gold. Plus, when you wanna back door late game, just teleport to the farthest minion in that lane and push the rest while the whole other team is on the complete other side.

: Good to use for catching an opponent who is running away, or a good escape move when you are being chased. However, it is not as good as flash in my opinion. Ex: You can flash out of Veigar's Event Horizon (if not already stunned), but you cannot run out of it.

MercyMercy: This is Talon's passive that allows him to do more damage on units that are slowed, stunned, or under any other crowd control effect. This helps because Talon has an ability that slows and also a move that silences.

Noxian Diplomacy: (Q) This ability damages the opponent severely, and also makes them bleed, which is like an ignite or poison, but you can see where they go. This ability also doesn't wait for your next auto attack to hit. It hits as soon as you press Q, which can be useful for farming. This move also works on turrets, so you should spam it when hitting the turrets or inhibitors.

Rake: (W) This move sends out blades in a cone, which immediately come right back to you, slowing any target in its path. This move will be your main move at the beginning, because it will be your best farming move and a great move to harass your opponents who are trying to farm. It's also useful to slow enemies that are running away from you.

Cutthroat Cutthroat: (E) This move instantly teleports you right behind your enemy and silences them. This move is great for initiating one-on-one battles, because they can't flash away quickly or use any of their abilities to slow or stun you. This is also great when chasing enemies. You just teleport to them, use rake, and then catch up and kill them.

Shadow Assault: (R) This move is your ultimate, which sends blades out in a circle and makes you become stealthed. Your next action (any action except moving) will draw all the blades back to you. This move can be used to escape, because when you are stealthed in this move, you become faster. This is also great for team fights, because it will hit everybody there. Just be careful with auto attack. If you want to get away, make sure you don't auto attack a minion and un-stealth yourself.

Your basic combo when faced against an opponent will be an E+R+Q+W combo.
COMBO:
Cutthroat + + +

The reason you use Shadow Assault right after Cutthroat is because the blades will hit the enemy on the way out and back to you. If you are still behind the guy when you use Noxian Diplomacy, then most of the blades will hit him on the way back to you (assuming you were still stealthed). Then slow him with Rake to make sure he doesn't get away and to do extra damage.

I always pick up a Long Sword at the beginning. Most people would pick up a Doran's Blade, because they start out with enough money and it provides more, such as health or lifesteal. However, I don't like it because it doesn't build onto later items. Yes, you could sell it later, but I don't like wasting the money. 3% lifesteal just doesn't cut it for me, so then later I get the Vampiric Scepter. This is able to keep me in a lane and at a good amount of health.

The Brutalizer is a pretty standard item for an AD champion. It provides a sufficient amount of armor penetration to defeat those who think they are smarter than you and get a bit of armor. Well they are not smarter than you thanks to The Brutalizer. Also, you can upgrade this item later game to get some more armor penetration, critical hit, cooldown reduction, and damage, but it's not really needed until you have all your other items.

Since we are going for a good amount of attack speed here, it is only wise to pick up the Berserker's Greaves. Especially early game, they can help you farm when you're laning, and some other chump is trying to take your last hits. I usually like to replace this item way late game after I've gotten all my other items with another Phantom Dancer, because it gives me a lot of movement speed and even more attack speed. So if you do that, you'll be just a fast, get more critical hits, and take out other champions faster.

The Frozen Mallet is a GREAT item for Talon because it slows the enemies with your attacks. This takes full advantage of Talon's passive, Mercy. THIS ITEM COULD BE SWAPPED WITH THE BLACK CLEAVER IN THE BUILD.

Next we have Black Cleaver. This item is very useful and gives you a good chunk of Attack Damage and Attack Speed at the same time. Plus, you get that bonus passive that helps reduce the enemy's armor.THIS ITEM COULD BE SWAPPED WITH THE FROZEN MALLET IN THE BUILD.

Then you'll want to get Bloodthirster. This gives you a huge chunk of Attack Damage, and also some more lifesteal. This item could be bought earlier in the game, in exchange for either the Black Cleaver or the Frozen Mallet because it is an item that stacks, which you could get earlier to be more powerful.

I love getting the Phantom Dancer. It helps when getting back into the battle after a death, killing someone faster with your basic attacks, or just backdooring or pushing a turret. You can kill someone extremely fast with this item, and if you're slowing them on every hit, they won't be able to get away.

Lastly, you get Youmuu's Ghostblade. This item is just to build off of the Brutalizer, and can be swapped with any of the other possible items (see below for details). However, this does give some pretty nice armor pennetration and ability cooldown, which can come in handy late game.

OTHER POSSIBLE ITEMS

Infinity Edge: Good item, gives a lot of Attack Damage, which could be very useful. Not as good as another Bloodthirster in my opinion.

Hexdrinker: If the other team has all 3 AP, you know what to do. Get all magic resist items, right? WRONG! This item will help build magic resist AND attack damage to kill those AP guys faster.

Wit's End: Also a very good item when facing an AP heavy team. Keeps the build in check with attack speed and attack damage.

Warmog's Armor: This is an item to get if you are dying way too quickly. With this and the Frozen Mallet, you should be good on health.

Last Whisper: Good if you still can't get enough armor penetration to kill those pesky tanks.

You're probably wondering why the Trinity Force isn't on this list right? That's because I hate the item. It costs way too much, and gets a little bit up in a lot of stats. Half of those stats aren't even needed for Talon, so why should he pay 4000 for stuff he doesn't need? The only reason I would recommend this item is for it's passive. But other than that, he could get all the other stats in different items for cheaper.

Early game is easily the toughest for Talon. Start with your Long Sword, and upgrade Rake first. This will be your primary ability early game because it will help you farm and possibly poke the other team, but it's not super long ranged so be careful. Talon cannot solo a lane, so I like to lane on bottom (or top if no jungler) and beat the other team to the bushes. If I have a fast teammate, we'll get there before both of the other team does, and we'll try a gank on the first person to come in the bushes. I'll use Rake (the only ability I have) to slow them while my teammate does a lot of damage. I might pop exhaust, because by the time I need it next, it will already be cooled down.

Now that that's taken care of... FARM FARM FARM!!! This is pretty much the only thing you can do in the early levels, and it's needed since Talon is so item dependent. Noxian Diplomacy should help you farm because you it doesn't need to wait until your next auto-attack. You simply attack right after you hit Q. Use this and Rake to help yourself to a lot of farm action. Try not to turret hug, because the turret will take some valuable gold away from you.

Get Cutthroat at level 4 so you then have all your moves. This is a very helpful move that teleports and silences the enemy you target, and can be used very usefully if the enemy overextends. Use this move so they can't flash away or to save your partner from a death from the enemies ability.

By the time I go back the first time, I usually have enough to buy the Boots, Vampiric Scepter, The Brutalizer, and maybe finish off the Berserker's Greaves. By this time you should be level 6. However, if you're not even close to dying in the lane, stay there and farm some more. Because as soon as you finish those first couple of items, you have to start working on your first B.F. Sword, which can be a tough transition.

At this point, you may have gotten 1 or 2 kills in your lane. Now it's time to go crazy. If your partner can handle a lane for a little by himself, you might wanna go gank middle or top/bottom. You can do some pretty descent damage with your E,R,Q,W combo. If you don't go for a gank, keep farming and wait for everyone to start pushing a lane.

By now, if you don't have your Berserker's Greaves, you are getting behind. But don't worry. You can still catch up. All you have to do is stay in a lane, farm, and watch out for ganks. Start working on getting your Frozen Mallet. This item will help a lot with your survivability because it gives you a big chunk of health. It also helps because your passive helps you do more damage to people who are slowed, and the Frozen Mallet reduces your opponents speed. After this, start working on Black Cleaver. Unless you have enough money, you'll have to start with a B.F. Sword.

Once you start ganking/pushing a lane with the rest of your team, be careful. I know you just got a big chunk of health, but your not invincible. You're actually very killable. People will target you because you can do a ton of damage to them. Try to go in after the tank on your team is targeted, and pop your combo, and do a chunk of damage.

Alright, now that you have most of your items, you can start wrecking people. When I go solo against other opponents one-on-one late game, I usually win 8 times out of 10. I like to put exhaust on them, do my combo, and start auto attacking with incredible speed. However, the team comes first, so try not to go alone to often, or you might die.

After the Black Cleaver, you should start going for Bloodthirster. With this item, you'll be able to land some great hits, and steal a good chunk of their life while you do it. Once you get that, it's onto the Phantom Dancer. Once you get this item, you can start to push lanes by yourself super fast.

When pushing a lane by yourself, you need to be very careful. I always have my eye on the minimap, which tells me which of the opponent champions are battling my teammates and which ones aren't. I figure out which ones aren't, and if I think I can't take him one-on-one, I try to lay low in the bushes until he appears. However, there aren't many people Talon can't take one-on-one late game. Be aware of the surroundings. But you will be able to push lanes extremely fast late game with this build. Backdooring is extremely effective when your team is losing, and can ultimately save the game. First, it makes their teammates retreat back to you before you take out all their inhibitors. Second, if they don't retreat, keep pushing until you destroy their turrets and ultimately, their Nexus.

http://leagueoflegends.wikia.com/wiki/File:Talon_CrimsonEliteLoading.jpg (For the Picture)

http://www.mobafire.com/league-of-legends/build/making-a-guide-101506#chapter1
Thanks to jhoijhoi for helping me make my first guide!

Mobafire, for letting me share my thoughts and ideas! Let me know if you see any mistakes or things that need changing!
Enjoy! :)