Crafting the last upgrade in each category requires you to find a rare, unique animal.You'll be near an ammo store, so you can restock if need be, and there are plenty of sharks just off the coast. The best spot to do this is north of the Welshore Wrecker's House outpost, on the northwestern corner of the first island.
It's easiest to take them down after you unlock the RPG hitting a shark with a rocket-propelled grenade will kill it in one shot, allowing you to swim out, skin it, and return to shore to nab the next one.
(You'll be doing this regardless, so you might as well get it out of the way as a benefit you'll unlock a lot of free weapons in stores.) After doing that, attack as many outposts as you can to both eliminate enemy patrols and unlock new Path of the Hunter missions. If you want to get a jump start on crafting at the beginning of the game, it's worth taking your time to travel the map and climb to the top of all the radio towers that you can access. Luckily, almost every animal you need to hunt will be marked on your map, assuming you've revealed it.
Of course, finding that prey might be a different matter. If you're quiet while you move, you shouldn't have too many problems bagging your prey. Luckily, the process isn't all that difficult, as the early tutorials will explain most of the basics: go to an area that has the kind of animals that you need to hunt, hop out of your car, wander around for a bit, find your targets, and shoot them. In order to load up with more goodies, you'll need to hunt animals and use their skins to make more bags for yourself. When the game starts, you're going to be grossly limited in the number of items that you can carry. Ready to get up close and personal with Rook Island's meanest denizens? Curious about the easiest way to silently take out an enemy outpost? Want to figure out how to unlock most of the game's weapons before you even begin the story? Ever wanted to kill a shark, but weren’t sure how? We've got you covered. Luckily, GameSpot's Game Guide will help guide you through all the ups and downs of the game's main storyline, and will offer plenty of tips for the side missions, as well. Well, Far Cry 3 certainly isn't going to break with that tradition, as you'll find yourself squarely in over your head as soon as the game begins. Be honest: have you ever seen any media that begins with a bunch of crazy twentysomethings having a crazy twentysomething lifestyle, doing shots of motor oil and jumping out of planes, screaming about Mountain Dew while punching a dolphin square in the solar plexus, etc., that doesn't end with some kind of horrible misadventure? People shooting at them, cannibals, alien marauders, a Dane Cook performance?