Here I have some tips every new changer should know before he/she starts.
It would be nice to make this sticky so we get less requests based on basic faults.
1. NEVER open up 2 Model edit applications or the WoW client the same time. This will destroy your files with a very high chance.
2. Best way to work with ME patches is to create all the folders and files of the patch on your hard-drive and compress the howl folder with MPQEdit.
3. Make often backups of this folder during you work on the files. If the files crash you can restore them. Create a robocopy script is a good way.
4. You have to putt changed files into a new MPQ file called patch-X.MPQ. X can be every digit or char form 0 to 9 and from A to Z that is not already in use of WoW. So if wow have a patch-2.MPQ you can not use the 2. The extension MUST be upper case .MPQ not .mpq! And dont fergett the minus sign between the word patch and the digit/char.
5. Extract all WoW data files to a folder on your HD. So you can search them easy and find necessary files faster. Do this in the right order. First all MPQs direct in the data folder common,common-2,expansion,lichking,patch,patch-2,patch-3 and then some from the language folder locale-enUS.MPQ, expansion-locale-enUS, lichking-locale-enUS, patch-enUS, patch-enUS-2, patch-enUS-3. Many files are contained in the normal and in the patch MPQs. So it could be that you find a DBC where the structure was changed in a patch and the old one crash your WoW if you use it.
6. Some parts of the MPQs need a ME fix if you want to change them. The Interface folder for example. If your patch file did not work, try this fix.
If you have some points I forget, post them. I will add them to the list.