the best champions to be assassinate are the mages you can kill the mage so easily and get feed
for the assassination you need speed and damage (some critical chance is good for his Q).
For the the first step of assassination is to get to enemy champion by flash or talon's E
then attack him and get his Q on the target.
If the target was escaping you can use your w for slow him and damage him to get him .
If you think he is to far from you you also can use your ultimate and get to him and use your exhaust to slow the target
If you think they want to gank you and you are in danger you can use your ultimate or your flash to escape or get to the target if you think that the target is far from other of his teammates you can get him then kill him and escape
The next thing is risking to kill and then die I think this isn't a good thing cause talon has low armor and magic resist so if the enemy get's feed the talon will be the easy target to kill

the best partners for talon are Blitz,Shen,Volibear,fiddle,ashe,leona
when the talon is with hist teammates better to get his E first then the other spells
i think the E is good because of you can get to the enemy fast and make an 1vs1 battle 2vs1 and win easily or you can get ignite and use your W to finish of an enemy then go and get the other one
The next thing for talon is his friends support if the enemy marks on talon he has no chance to get out of it with or with out flash so better to your friend goes first(don't go with a mage)

Thank you
if you have any question comment me
Good luck
KIHO

TALON against FIGHTERS
I think you have low chance to defeat or kill the fighters then runaway so most of times you have to run away and escape from them.
The first ting is to have some range and distance from them to make your escape.
The next thing is using flash or your ultimate for escape and running away you also can use your E on minions or use your W to slow them.
Talon against heavy ranged dps
Most of ranged hasn't any stuns or slows so you can escape for them with your W you can slow them and get out from them or use your exhaust to slow them.
if you think they don't have any cover and you have full health you can use your E or flash to get them and use your W and Q in same time for damage him so much then your ultimate for scare them then so they will fall back and you have so much free time for making your escape in safe so easily.
thank you
KIHO