As soon as you finish The New Kid in Town, you will be able to freely explore South Park. On the north end of town will be a shop called Jimbo's Guns. Go inside and talk to Jimbo, then buy the book titled "Hunter's Guide to South Park Wildlife." Once you do, Jimbo will ask you to hunt down seven creatures around the town, giving you items so you can lure them out.
Note that for each creature killed, you can return to Jimbo and get a reward, with an overall reward for completing the whole quest. You won't be able to complete the entire quest until late in the game, as one of the creatures is in a late-game area. Your reward for the whole quest is becoming friends with Jimbo and Ned, as well as Jimbo's Key to open the chest in the rafters above Jimbo.
Rapid Junkyard Dog
The dog is located right outside of Kenny's house in the southeast corner of the map. There should be a deflated tire to the right of the house, which is where you place the item. As for the dog's battle prowess, it's a pretty standard fight, so you shouldn't have too much trouble with it.
Farm Cow
The Farm Cow is located at the barn in the upper right corner of the map. There should be a cow bell hanging on the front gate, which is where you place the quest item to lure him into the open. You don't even have to fight it, since hitting the cow with your weapon will defeat it.
Penis Mouse
The Penis Mouse is located in the sewers, which means you will have to wait until after finish the Alien Abduction quest to get to it. Go to where the generator is and left behind the wall there to find Mr. Hanky's house. Continue past the house and go up the ladder to the left of the house.
Use the walkway in the back to go to the right, past the ladder and break the boards blocking a switch that opens the gate just to the left of it. Climb the ladder and the Penis Mouse location is right to the left. It's much harder to find the Penis Mouse than to kill it in battle, as it's a pretty standard fight.
Fruit Bat
The Fruit Bat is also located in the sewers, but in the cave portion of it. You should see a big opening in the background in the area with the generator. It shouldn't take long to navigate to that area, which will lead into the cave area. You know you are in the right spot when you take a ladder down and see a crab person in the back banging on some drums.
As for the location of the Fruit Bat, continue past the crab person and you should see a path that goes south and west, leading to a dead end. Place the item to make the bat appear and then kill it, which is a pretty straight-forward fight.
Mutant Bacteria
The Mutant Bacteria is located inside of the school, in the basement, which you will travel through on your second visit there during Attack the School. There will be a side room you can enter, with some petri dishes on the table, with one of them having some kind of mold. This dish is the one you place the item in to make the enemy appear.
There is only one thing to note in regards to the fight with the bacteria, which happens once it gets low on health. If it does drop below this, then it's likely it will split into three enemies, making you have to work harder to kill them all.
Barking Spider
The Barking Spider is located in Canada, which you travel to whenever you're doing the Forging Alliances main story quest. On the map, you should see a spider's web in the upper right, which is where you place the item to get the creature to appear. The spider has a lot of armor, so using abilities or weapon attachments that lower this will be extremely helpful. Otherwise, the fight is pretty standard.
