Hiya.

There is no easy answer. You just have to practice, practice, practice! Unless you are a "natural" at 3d modeling, it will likely take you upwards of a year or so to get real good at non-organic (re: non-"human/animal") modeling, and probably double or tripple that for organic modeling.

The methods for modeling are more or less the same, regardless of package. However, if you are a total noobie at 3d, learning the ins and outs of your chosen software is the first step. All 3d packages out there have tutorials that come with them I'm sure (trueSpace, blender, etc.). Go through all of those. Then hit the net for others. There are too many to list, just search and read. There are some places that sell tutorials or have "premier support" monthly payment deals that allow access to more/better/advanced tutorials. Here's a few links to get you started (some are package-specific, others more general):

http://www.3dbuzz.com/vbforum/sv_home.php
http://www.zoorender.com/
http://www.secondreality.ch/
http://www.3dtotal.com/
http://www.deathfall.com/tutorials.php
http://www.kurvstudios.com/
http://www.3dkingdom.org/index.php
http://www.poopinmymouth.com/index.htm
http://www.thehobbitguy.com/Tutorials.html