Talon's most crucial stage of the game is his laning, where he needs to build an advantage over the enemy either through items or kills.
Talon does benefit greatly from a solo lane and obtaining his ultimate faster, but his purely offensive kit can make it difficult to lane versus many champions without support. The champion he tends to do best against one-on-one are the squisher types, like mages or carries, his high burst damage easily overwhelming them.
Rake is your best tool in the lane, allowing Talon to last-hit and harass from a decent range.
Mercy allows Talon to deal more damage with each auto-attack on enemies that are affected by crowd control effects, therefore, laning with a champion that has decent early crowd control such as Gangplank will benefit Talon's early damage.
Talon's high burst and Mercy goes hand in hand with most jungler's CC effects.
Try to perform this at least once prior to reaching level 6, so as to force opponents out of the lane due to the threat of dying to Shadow Assault.
Talon is a hard champion to catch. Use Rake to slow pursuers, and Shadow Assault for the stealth and high movement speed. Change your path direction during stealth to juke and confuse your enemies. But keep in mind that the enemies can see where your blades travel when your stealth ends. So using the ability just to run can sometimes be better than running into the enemy jungle while trying to juke the enemies.
Cutthroat can be used to ambush enemies behind thin walls, if they are close enough and you have line of sight. Alternatively, you can use Cutthroat on a minion near an enemy champion for a quick entry into battle.
Noxian Diplomacy resets the autoattack timer, so use this ability after autoattacking to gain 2 hits in sucession.
Shadow Assault can be used both defensively or offensively. It can be used as either a tool for chasing an escaping champion or escaping a gank.
One way to ensure Shadow Assault's return hits your target is to use Cutthroat, immediately ending the stealth and positioning yourself such that the blades are guaranteed to hit.
Talon's basic move combo requires him to activate Shadow Assault then closing the gap with Cutthroat which will devastate an enemy. If this does not completely anhiliate an enemy continue with Rake to chase an enemy and if they still have not died, finish them with Noxian Diplomacy.
When you are ganking/chasing enemy that has Flash or a similiar escape tool (Ezreal, Gragas etc.) dont use your Cutthroat immediately, but simply run near him until he wastes his ability. However, be careful when he can jump over walls as you need vision of them to blink to them with Cutthroat.
However The Black Cleaver requires you to hit an enemy 3 times with autoattacks or on hit affects before applying the full armor penetration. In most cases Talon should be able to assasinate a target with his skills alone.
Frozen Mallet is worth considering, as it grants Talon survivability and a slow that allows him to constantly proc his Mercy passive. Do keep in mind that Talon is an assassin with a lot of escape spells, so your gold is probably better invested in damage rather than health, at least in early to midgame.
Combination of Frozen Mallet and Guardian Angel will make you tough enough to participate in teamfights without any problems. When you get focused, Guardian Angel will prevent your death, with a little help of your team. However attack damage is a first priority before getting much more tanky items.
Atma's Impaler is a excellent item for the endgame, granting a good amount of survivability alongside a fair amount of extra attack damage. The critical strike chance, while unreliable also helps in kill efforts.
Talon is fairly squishy and vulnerable to harrasment during laning phase. Use this to your advantage but be aware that his Cutthroat and Rake can easily turn the engagement in his favor.
Talon's reliance on burst damage is a heavy weakness against targets he can't quickly kill. Fighter champions tend to beat Talon, being durable enough to survive his combo and do enough damage to deal with Talon's squishy self afterwards - fighters with innate sustainability abilities in particular will survive Talon's combo and then just heal themselves back up.
Investing in True Sight items might be worth it to prevent Talon from escaping ganks or initiating on squishy allies of high priority for the team.
Watch out for his Noxian Diplomacy and Cutthroat combo. It can deal significant damage and combined with Rake and his passive Mercy will deal significant amounts of damage within a few hits. Zone him when you can and press the advantage