Id suggest doing some form of modding to begin with, ie Quake3-2, Halflife, Unreal Tournament Player models... there the best place to start since thre relativly easy to incorporate into there respective engines. One of the major problems I see alot of beginners doing is useing overly complex models for things.
Optimisation mixed with conservative and well placed detail for effect and correct mesh deformation is the Key. If youve modeled a face in 300 polys, and you could remove 100 of them and still have basicly the same shape, remove them... since thats 100 less polygons that can be used else where, or on another model all together. Every polygon has to be culculated by the PC, the less there are teh faster it works out what has to be shown on screen and the quicker it can get on with the next frame... ie faster Framerate.
A simple rule of thumb I picked up from others, is that if the detail on a model is less than 3 finger widths in size on the life size version of what your modeling that detail should be shown on teh texture rather than geometry, how ever things like teh face should us a 2 finger width rule, as the detail there is smaller but neccesary in certain models.
Above all dont slap a few geospheres and cylinders together and say can you use this, as the pack in Geometery tools in 3d programmes are no good for modeling low poly, unless you use the base mesh to get your vertex count up and running quickly (at which point you would then move vertices and edges around, kinda like modeling with a lump of clay). you might have a \"wicked\"mace but the polycount would swamp even the most hardened PC. Pack in Primitives in 3d programmes are designed for high polygon modeling, which is what those programmes are mainly and actualy used for (shreik, JP etc) not Low polygon... You should use the mesh edit sub-Object modifier (or its equivilant) to make your models as you start by making the vertexs you need and you can easily controll them rather than having to deal with a huge amount all at once.
what im saying is... its all about the polycount...
PS:- oh and dont throw togther a Poser model image and say, look what i did... Poser is what Poser is... you assemble a model from pre made bits, adjust there dimensions and pose it, you havent made that model from teh ground up and its polycount is insane, not to mention its just down right cheap and nasty. Poser isnt a 3D modeling tool... its a gimmic. Poser skills are not 3D modeling skills...