Not much to say, really. I mean, just try it out. Maybe you won't like the squishiness much but... I mean, damn, you can melt anyone and anything out of your way with this. Doubts, ask. Just don't be a douche.

For as long as you don't have your ultimate, avoid direct combat. Sometimes, poke with the Rake, but don't risk much, and save mana. You're as soft as jello in the gamestart. Some mid-laners will attempt to keep you at bay. They are usually just as soft as you, so as soon as you get your ultimate Shadow Assault, obliterate them, but again, don't risk it all for kill greed.

Talon can do efficient, quick ganks on both other lanes. Good coordination will always result in a kill. Just don't let your own lane fall, OK? Also, beware wards. If you get crowd-control stuck at a low level because they intercepted your gank, you're dead meat.

In end-game team fights, there are roughly two situations:
[*] Offense: Always let others start the team fight. The least crowd control you get on your head, the faster they'll be dead. If you jump head-first into the fray, you'll be piled, so only do that if you intend to give just a single blow and then use the ultimate to get out. That kills most low-health ADCs.

[*] Defense: Try to circle around them, and look for key targets. As soon as they get busy with a tower or someone else in your team, kill the helpless poor thing. Check if you've drawn too much attention. If you did, get out. If you didn't, or the threat is minimum, start a slaughter.

Besides of that, all else is attention and coordination.

Extra hints:
[*] You might even think "1 second of silence for the cutthroat? Useless..." Well, try using it on an ulting Nunu & Willump or Miss Fortune. You'll certainly piss them off. But yes, the fact a cut to the throat doesn't deal any damage really doesn't make any sense.

[*] See that Xerath? Don't let that mobile turret poke you. Just don't.

[*] There are some points in the jungle that, when you hit a mob with the Rake, they become temporarily visible. They're good "tow points" for the cutthroat, technically giving you an extra Flash.

[*] Try dodging an Ezreal/ Fizz/ Lux/ Draven's ultimate skill with the cutthroat. It tastes sweet.

In early game, it's a bit of a challenge. You probably won't deal significant damage with the Rake for that, and it draws quite a bit of mana.

Plan every Rake throw, and farm as much as possible, SAFELY. Avoid getting poked in lane phase, unless you have a "fake-weakness" plan in mind.

But don't worry much about that. The money you'll be getting in lane phase will be mainly from kills and ganks. Once you bought Infinity Edge and, depending on your rune layout, you might need an extra B. F. Sword, you'll be reaping minions with a single Rake throw.

Pros:

[*] You can kill virtually anything Tryndamere-style. Don't risk 1x1 with Tryndamere until you've got your build complete, though.
[*] Lifesteal is high enough to keep you alive until your target is dead, in team fights (well, it won't take too long to kill the target, so I don't know why I said that.)

Cons:
[*] Even though you have a lot of damage making lifesteal keep you alive, if you get crowd-controlled by everyone, you'll die. Plan your jumps carefully, and use Shadow Assault with the primary intent of ESCAPING, not KILLING.

[*] Oracle's Elixir, vision wards, Lee Sin's E skill and Trundle's totem. These things are dangerous. Think twice before going into a fight when these are present - you might not get out of it.

I won't put a rune layout. But know one thing: Critical Chance runes are useful. If you get a critical strike with Noxian Diplomacy, you'll deal more damage than a critical strike from Gangplank's Parrrley, and scare the $#%t out of your foe, in early game. It will also make sure almost all of your attacks, in late-game, are critical.