Here are two links that explain alot (not all) taglines in XML files:
http://civ4wiki.com/wiki/index.php/Xml_files
http://modiki.apolyton.net/index.php?title=Reference_xml
they are not complete and you sometimes have to cross-reference them to get all (or more in-depth) info
NOTE: be warned sometimes the links are not always working.... retry them at a later time if they dont initially work
to create a new mod just make a new folder in your:
CIV4(
or whatever you named your main game folder)\Mods folder
then create the correct/corresponding folders with the files you are going to edit/replace
for example... lets say you are going to edit/change the XML file
CIV4UnitInfos.xml file
first you go copy that file located here:
CIV4\Assets\XML\Units Folder
copy that file
then go to your
CIV4\
Mods Folder
create a new folder (whatever you want to call your mod)
CIV4\Mods\
NewMod folder
then create the folders that follow the original path
CIV4\Mods\NewMod\Assets\XML\Units Folder
place the CIV4UnitInfos.xml in the
Units Folder
then edit this copy of the CIV4UnitInfos.xml
there are three ways to have your mod load up
1) start the game as normal... then pick "advanced" then pick "load a mod" and pick your mod
(for my example it would be "
NewMod")
2) Edit CivilizationIV.ini config file
Find:
; Specify a Mod folder (Mods\Mesopotamia), '0' for none
Mod = 0
using my mod name example change that "Mod =" line to
Mod = Mods\NewMod
this will load the mod everytime you load the game...
3) create a shortcut of your CIV4 startup game
Secondary click on the new shortcut and select "properties"
See the entry that says:
Target: "C:\Civ4\Civilization4.exe"
Using my example change it to:
"C:\Civ4\Civilization4.exe -mod= NewMod"
now this shortcut will load up the mod!
(You can make multiple shortcuts to load up different mods too!

)
NOTE: If it doesnt work ...try removing the quotation marks ("")
hope that helps
