http://boards.pbe.leagueoflegends.com/en/c/champions-gameplay-feedback/Rw3iGKEj-new-masteries-build-tips-and-theory-crafting
It's pretty straightforward really.
Ferocity is for AD Damage, or for AP Mages who have easy-to-apply DoTs (Cassiopeia and Brand and Swain off the top of my head). Deathfire Touch does NOT work on Talon's Q though.
Cunning is for AP Mages or for AD Assassins (Talon, Zed, maybe Quinn) or Supports who don't need to be tanky. You can choose between Stormlord's Surge (35% movespeed for 3 seconds after burst) if you need to disengage after assassinating someone, or if you want insurance of killing someone, Thunderlord's Decree is also quite strong (currently bugged to scale with 20% AP instead of 10% in-game, at least according to the Scoreboard Tooltip). Windspeaker's Blessing is OP for supports that are passive and can heal often (Sona, Soraka, maybe Nami) while Thunderlord's Decree is good on supports who want to win trades (scales better with levels than with AP anyways).
Resolve is for being tanky. There's literally no other reason to go deep into this tree.
The exception is usually jungling since there are a lot of different ways you can go: I personally like 12/6/12 just for safer clears but if you want stronger ganks you can go 12/18/0.