Talon is an "assasin" and he can not fight like a warrior. However, it is possible engage in combat face to face, all depends the circunstances... but... anyone that use Talon must know "who" are their objetives. Talon must always prioritize squishies first and weakened tanks/warriors/off-tank like Irelia, nasus, etc, in second position. Talon can deal a big amount of damage in a short time, appearing by surprise and disabling the enemy enough time to launch the skills combo. Play Talon requires: pacience, strategy, team play, acute vision and the most important predator instincts ;P

Start with Doran's Blade, this will give you extra hp (just in case..), damage that is good for when you throw the knives (the difference can be appreciated), and a little bit of life steal.
Why not Boots?... I tell you why, because now you should let push, so is better hit more hard with your knives, be cautious, weaken your enemy and wait for the right moment to gank (if your jungler is efficient you can have a good start).
As second item always is good get Boots, now yes... because many, many times at this point an incident can happen, a team mate gank, a little fight somewhere near, so now boots yes make the difference for: to chase or run of being chased. Try to buy too The Brutalizer.
Third, complete Youmuu's Ghostblade and Ionian Boots of Lucidity, with this you can start to get fun :) (by the way.. don't forget to activate Youmuu's active ALWAYS).
Now is time to get money for: B. F. Sword, because you need damage, without damage.. you fail a little bit in your ganks, getting this item now is perfect and in the right moment too.
Ok now you can buy Cloak and Dagger, this will give the attk speed necesary for to exploit your Cutthroat, remember that this amplify your damage for the next 3 sec. Also you get tenacity that is necessary.
Let's finish completing your damage stuffs, so play a nice game and while you do it, buy: Infinity Edge and Bloodthirster.
The last item is optional, but i preffer Banshee's Veil because when i jump to an enemy, I can evade the first skill and most times it's some skill to snare me or some annoying thing.

For masteries you should take offensive, I like 21/9/0, remember, that you are like a ghost, you just appears from nowhere, do all the damage posible and in the short time. Also 9 points in the defense tree gives you some survivality and hp ;)

Just one simple thing: ONLY LAST HIT TO MINIONS!! and look the map, that is your farm area.
Why? because:

• You can farm while you give last hit to minions and weaken the enemy with your Rake in passing.
• You don't run the risk of being gank.
• You give the chance to your jungle to gank.
• You want to push? do it when your enemy is dead.

I chose these two spells for this reason:

• Flash: will save you like nothing else, sometimes you need to retreat when the focus is hard. This makes the enemy team lose the target, confuse them to wich target now, and gives you the chance to come back to the battle, helping your team to snare em, etc or just escape to don't give a kill.
• Exhaust: I think is better than ignite in many ways, but the most important is that allows you stop that AD carry that seems to be unstoppable.

Now this is important... how to explain it.. OK, Starting from the fact that every game is different and anything is possible, as a general rule your point of attack will be starting from behind.
Imagine that a TF is about to occur, you will see that their carry/support (whatever) will be protected for all of them to no one can get through to him. This champion is your primary objetive, but if you go for him too soon, or your team fail, then.. you just die and quick..
In any other situation keep present always in attack that champions with low hp, that deals a lot of damage, you should gank em, kill em, persuit em, found em, hunt em.. etc.
Keep in mind that tanky champions you dont have nothing to do...

This is the order of using the skills in a fight for a perfect exploit of them, and do the maximum damage, including your ulti knives.

Talon is the perfect squishy assasin, for me is one of the best and more fun champions in all league of legends.
I hope you enjoy my guide and have fun ;)