Well what guide exactly are you looking for? m2 version converting, or creating
new items in general? Or both? Because I've already given you a spot-on guide
for the m2 conversion which is required to make sure your items are compatible
with 3.3.5a.
For the creating of new items, I'm not sure if there's a guide for that. You need to
edit the dbc files. Item.dbc and ItemDisplayInfo.dbc. Item.dbc is not required but
if you don't put a proper entry into that one, you'll get the red question mark icon
on all of your items. ItemDisplayInfo is just the creation of your new DisplayID
which is what you'll have to use when you create the item in MySQL database.
Once you get a hang of dbc editing you can teach yourself to do basically
anything just by checking out the documentation on the WoW dev wiki. It's trial
and error, and using Blizzard's content as a reference will take you a long way.
The fun part about modding comes from research and trying new things ^^
http://www.wowdev.wiki/index.php?title=Main_PageOn the left you'll find "tables == WotLK" that has almost all of the dbc files. Might
have to scroll down a little bit because the formatting on that website is fucked.
Edit: Just noticed the 010 Editor binary templates link is dead. Here's a new one: