War3 Model Editor cannot directly make scratch models aside from particle emitters, as it has no vertex addition functions.
For free Warcraft 3 scratch modeling, you can use Oinkerwinkle's tools:
http://oinkerwinkle.com/tools/download.html
He has a couple of tutorials for scratch modeling over here:
http://oinkerwinkle.com/tools/tutorials.html
There is also MDLVis, found
here (click), which is a simple model editor for wc3 modeling.
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However, there are also some tools that have exporter scripts for Warcraft III. One example is GMax:
http://www.turbosquid.com/gmax
It is free and works decently. There is NeoDex which acts as an exporter for it. I also recommend
Milkshape, as that has a simple interface and works great. (But it costs $20 or something. It has a trial version though)
For tutorials on Wc3-related modeling, I suggest referring to any of these:
http://www.hiveworkshop.com/forums/3d-modeling-tutorials-282/
http://world-editor-tutorials.thehelper.net/magos.php
http://www.wc3c.net/tutorials.php?f=429
http://www.hiveworkshop.com/forums/modeling-animation-276/
Enjoy, and good luck!