just try searching 4 some basic modeling tutorials 4 Gmax/ similar. most char tuts tell u 2 start by making a cylinder & then to expand it with extra vertices going up- ie make the leg first, then the abdomen, torso, neck & head. then stick a horizontal arm on the side, then mirror the mesh and attach the 2nd half to the first. the hard parts making the bones and getting the anims to work (not to mention mesh details!)

a good start would be the Wiley Gmax Bible by Kelly Murdoch- it tells u everything about Gmax (& some basics about SiegeMax & the DS Editor) unfortunately it costs a fortune & dosent actually tell u how to model a char. 

an Andalite (-if its from the Animorphs books u missspelled it)/ centaur type char for DS would be pretty cool . the best i ever managed to do was to give the Droog char armor by placing his mesh on the farmboy skeleton and then 'painting' each bone seperately for the anims to hold. then i used RefObject to drop in a second farmboy mesh with armors #1-7, deleted the head, hand and feet and merged it with the Droog mesh. it worked with the boots an gauntlets too, but there were only 3 or so helms so i figured f    it.

if u want to make a composite char, like Xaa s' Ratboy/Lactri spidergirl), u can do this using only Skrit, na? (ok lame joke) but thats probably even harder to learn than modeling.

long-winded & late, but i hope it helps