Same as Graf - though additionally, trying to make a humanoid or gun for your first model is going to be very difficult. I don't think I could make a good human model now, to be honest, never mind when I first started. I wouldn't get too disheartened.
Humans are so... inny-outy-bendy and curvy. I'd be inclined to start with things which are as close as possible to being boxes or cylinders... so... a low-polygon spaceship is just a box with three triangles stuck on it... and a truck is an L-shaped box, with another box on it, with a bunch of cylinders underneath it etc.
To pick some easy ones from the tracker, look at :
Envelope : Put that texture on a very thin rectangular box
Leaflet : Make a flat rectangular box, make 3 or 4 lines through it, and bend them up and down alternately, then stick a texture on it
14mm AP : That's mostly just a box. A few bits stick in and out, but it's mostly a box. Stick a texture on it.
Metal case : A box with a texture on it.
Anyway, those kind of things would probably be far more suitable for first modelling attempts, and are obviously easy to do when compared to making a human. In low-poly models like this, the texturing is probably more important than the modelling - so make sure to brush up on your photoshop skills as well. With some of these models, you can 'bake' the sprite over the model, then fill in the missing bits afterwards.
