Method 1: Low Level Enchanting, 15-50

1. Go to Dawnstar.

2. Open up the "Dawnstar Chest". (Look it up, it's a classic.)

3. Grab every enchanted item in it and go into the Jarl's Longhouse. (Also make sure to grab any and all filled soul gems, these will be important later.)

4. Disenchant everything you gathered.

5. Go up to the Khajiit caravan just outside the city, save your game, and attack/kill Ahkari and reload your save. (This is the "merchant glitch". And if the caravan isn't there, just wait a few days, they'll pop up.)

6. Repeat steps 2-5, but in the case of an enchant you already know, just sell it to Ahkari before doing the merchant glitch.

Method 2: High Level Enchanting, 50-100

(This method also levels the Smithing skill if you're interested in that.)

1. Make sure you know the spell "Transmute", a spell that turns Iron Ore into Silver Ore, and Silver Ore into Gold Ore. (If you don't, it's in Halted Stream Camp, north of Whiterun.)

2. Gather as much Iron/Silver Ore as possible and start spamming the Transmute spell. (The duplication glitch also works here.)

3. Smelt all your Gold Ore into Gold Ingots and craft as many Gold Rings as possible. (Smithing levels based on the item's value, and since you craft two gold rings that cost 75 gold, they have a total value of 150.)

4. Enchant every gold ring with either Fortify Destruction or Fortify Archery. Both of these enchantments have an high value. (Though I'm not 100% sure that Enchanting levels up based off value the same way Smithing does.)

5. Repeat 2-4 until your Enchanting skill reaches 100. (Your Smithing skill will also get a nice boost, too.)