Talk to Guard Leolin in the Northern Overwatch to begin this quest. This is a level 4 quest.
The Perfect Cut
The Dulari goes on and on, doesn't he? Let me tell you something important, instead of his talk about "pure knowledge". Every time you leave a secured area, you're just another empty pair of boots. They've had you focusing on individual targets, right? You need to practice against as many opponents as you can. See those piglings, to the south? Excellent practice for what's over the next rise. I'll watch your moves and let you know when you're ready to move on.
Accept the quest:
The Perfect Cut
Clean Kill <0/10>
Practice fighting large groups - against piglings
You can mark creatures on your map by clicking their names in the quest log. Press "L" to open the log. Locate the quest on the appropriate tab (in this case, "Zone Quests"). Then note that the monster name, "Piglings" in this case, is a hyperlink. Click on it, and it will mark their locations on the minimap. If your mini-map is not up, press "N" to show it again. That works for any quest, not just this one.
You should see plenty of piglings marked to the west. Head to the clearing, and start slaughtering them. They are easy to kill, but come in big groups.
Once you have gotten enough kills, return to Leolin in Northern Overwatch for his assessment. He tells you it was some find butchery, and not to feel bad about it - those pigs appear out of nowhere in the blink of an eye. Dulari says even though they're not native to the island, something about this area lets them thrive.
Your reward includes Swineherd's Wraps if you are a sorcerer, mystic or priest, Swineherd's Gloves if you are archer, warrior, or slayer, and Swineherd's Gauntlets if you are a Lancer or a Berserker. Make sure to equip them if they are better than what you are currently wearing.
This completes the quest, "The Perfect Cut".