Marks of Prey is a PvP item you need in order to get reputation with Talon's Vengeance, and at honored you get an item that awards this on kill in battlegrounds. This means it will be possible to farm it very easy, because it does not require you to kill players.
The fastest way to farm them at the moment is to go to Alterac Valley and kill low-level mobs there. They die extremely fast, and has a normal chance of awarding the Mark of Prey! With this method you should be able to get to exalted really fast.
The downside to this method is that you need to be at least honored in order to be able to get the Marks of Prey from battlegrounds, and getting reputation to honored can be a chore in itself.
If you still have not unlocked the faction, check out our guide to unlocking Talon's Vengeance.