"Hello everyone" as i like to say, I'm Hellfi, a random guy you may encounter on EUW. I'm not ranked, i'm not playing like a pro, but i'm having fun instakilling carries without them even noticing it.
Talon is usually Mid, or Top, but i really like the darkness of the jungle. Talon have an awesome gap closer and a powerful burst which allows awesome ganks.
He is an assassin, build him damage, not tankyness. (that allows some excitement while clearing Buffs camps :D )

Noxian Diplomacy(Q/A) allows you to autoattack twice, activate it right after you hear the first attack, proc on turret, make usage of madred, max it first : it cost less mana and the cooldown is shorter than Rake.
Tiamat and Ravenous Hydra Actives have the same effect allowing you to autoattack 3 times in a heartbeat, enough to stop theirs.

cutthroat(E) can be used on minions if your target is too far to reach them and you will be able to Rake their back. It's still better to wait to get in range with the help of Ghost
Use it to start the big monster to farm the camp faster. The bonus damage proc on Smite.
You can interrupt channeling of spells ( Katarina, Caitlyn, Miss Fortune, Fiddlesticks, Nunu & Willump, Malzahar, Galio...) with the 1 sec mute.

Rake(W/Z) is used to farm the jungle and slow your target ( mercy), max it second : the cooldown is always 10sec, you can only use it twice on camps, that's why we max it second.

When to use Shadow Assault(R) :

• to finish off an enemy if a bit more burst is needed.
• to flee (the cooldown isn't that long (75sec level 1), better save your life with it).
• in the middle of the ennemy team after you jumped on their ADC.

About your ult : While being stealth, activation of Ghost makes you become visible. Use Ghost before your ult for maximum speed. The blades are going to indicate where you are at the end of the 2.5sec, don't try to juke by going into enemy territory, they will know you're there.

Early :
Farm the jungle. you can't gank before level 4, but you better get boots of mobility before even trying.

Mid :
Gank often, ask if wards have been put down and where they are. You want the ADC and the APC to fear you. :)
Ask your Mid if he wants the blue buff, you don't really need it after you got Hydra.

Late :
KILL THE CARRY, yep that's it. well Talon is an assassin.
Run around their team and catch him from the side.
You want your eyes on him like if it was a cookie and you were the cookie monster, awesome metaphor.

Your combo should be :
Ghost when you go for the kill > cutthroat > Rake > autoattack > Noxian Diplomacy(autoattack) > Ravenous Hydra(autoattack) > Shadow Assault to GTFO
And when you're back to safety press Shadow Assault again or just wait.
In midgame the carry is dead after your burst, in late they bought Warmog's Armor and similar, you may want to finish them by autoattacking, you will probably kill them, but you will certainly die. Judge the consequences.