Candy Corn is a very common reagent used in many different Halloween Events this holiday season. It's not only used for the monthly achievement and some of the festive activities but it is also used in tradeskills for different holiday recipes across every profession. Farming for Candy Corn is actually pretty easy regardless of where you go. It can spawn in any zone and shows up as a mine on your minimap. Using that same logic you'll need a mining pick to mine it.
Much like other mines in the game the Candy Corn nodes can come in two different types, Raw Candy Corn which is just a normal Candy Corn mine with the common 3 ticks until it's depleated and then you have Rich Candy Corn Veins which work like Rich Ore Mines. Usually you can wack this thing 9 or even 12 times before it's depleated. There are a few different places that are really good for farming Candy Corn, most of which are listed below.
Now the lower level farming locations consist of Blazeridge Steppes and Dredgehaunt Cliffs. These two zones are 40 - 50 and have a huge spawn rate for Candy Corn as well as other highly valuable resources such as Gold Ore, Seasoned Wood Logs and other Chef consumables such as in Dredgehaunt (Rosemary Sprigs) Blazeridge (Chilli Peppers, Dill Sprig). Both of these zones also have very few mobs that will get in your way when farming unlike the higher level zones where mobs will swarm you.
Now the two end game zones that are good for farming Candy Corn are Cursed Shore and Malchor's Leap. Both of these zones have all of the endgame crafting materials (Mithril Ore, Elder Wood Logs, Orichalcum Ore, Omnomberry, Orrian Truffles, Ghost Pepper, Ancient Wood Logs, Saffron Thread) etc etc . They sell for about the same amount as the aforementioned materials from Dredgehaunt and Blazeridge so it is really entirely up to you on where you want to go gather at.
Below are written guides as well as video guides for each of these farming locations.
That's really all there is to farming Candy Corn. If you're below level 40 and still want to farm for this stuff then you can also do the noobie zones like Queensdale, Wayfarer Foothills, Caledon Forest, Metrica Province or Plains of Ashford. However I strongly recommend you go with Plains of Ashford, Caledon Forest or Metrica Province since in these zones you can get Vanilla Beans which are used in Baker's Wet Ingredients, used in making some extremely good Magic Find foods.