This exploit guide will show you how to edit your cache and turn an item into any spell you want to use. Only items with white unusable items like Reagents or mats like Leather, or Enchanting mats etc. I recommend using Reagents that way anyone can get them, and there's plenty of reagents to choose from.
Note: This guide is not catered for random noobs that just want their hand held through the cheating process... you actually have to use common sense... I'm not holding your hand like your mom.
This also isn't guaranteed to work on your server, although it does work on most.
Alright, so first things first.. go create a cache file for your server that you want to edit. All you have to do is log onto your server and go and collect the items you want to edit, I recommend hitting up a reagents vendor, PLENTY of items in there you can hack.
Once you've bought or seen the items they will be stored in your cache, so just quit your game and open up the cache file (World of Warcraft > Cache > WDB > enUS/enGB > itemcache.wdb). You'll need a Hex editor in order to open it.. just google for a free hex editor and you'll find one pretty easy. I'm on a Mac, and i'm using an app called 0xED.
Next, now that you've opened up your cache file, go find that item you wanted to edit, I commonly use a Holy Candle for my first change, then Wild Berries, then Symbol of Divinity (All from the reagents vendor). My app has a search bar, if yours doesn't, then just Control+F it.
Now that you've found where it is, you'll need to know what to put there, so go grab the spell ID of the spell you want to use. Then use a hexadecimal to decimal conversion site to find out what the spell ID is in hex. (Or do it in your head if you're a crazy genius :P) I used hexadecimal conversion, convert decimal to hexadecimal
Now, you've got a number in hex, what you have to do is switch around the first two digits and the second two, so if I had 5CDF show up in the conversion, i'd change it to DF5C.
Now grab that hex you just made and go back to the item you found in your cache file. Go look for the big gap of 00 00 00's under the item you searched, everything about the item is in hex under it until the next item, keep going down and down until you see the start of the FF FF FF FF's, once you get to the start of them, count ten 00's back, you'll be placing your hex on the 11th and the 12th spots.
Now that you've got that done, save and exit the program, if you leave it open WoW will change it, and you can't edit a changed file or everything will get borked up, so everytime you want to reedit this cache after playing WoW (You don't have to do this if you don't open WoW) you have to close the file and reopen it, WoW must ALWAYS be closed when editing the cache file, or it will mess you up.
To use the spell, find the item you edited and just right click it like a use effect, you can bar it as well and use it there.
That's all, have fun. Any questions feel free to post them, I'm only answering PROBLEMS or questions, not "how do I do this.. ", the guide explained everything pretty well.