Select the bottom polygon on one of the arms. From the top view, it should look like a diamond. Extrude this polygon about -50 cm along the Y axis, then delete that polygon and merge the extra points (four points should be eliminated). Move those bottom points away from the body so that the upper arm is angled away from the chest. Repeat this process for the other arm. Now for the forearm. Extrude the bottom polygon on the upper-arm, then delete that polygon and merge the extra points. Make the forearm wider than the upper-arm. Be sure to look at it from all angles in the preview. When you're happy with that arm, make the second arm. Remember, this is just the upper half of the forearm; it gets thinner at the wrist. Extrude the bottom polygon again, and make the other half of the forearm. Again, remember to delete the polygon you extruded and merge the extra points. Make it skinny at the wrist, and once you have it how you like it, repeat the process on the other arm. Once again, extrude this polygon to make the hands. Just to keep it simple, I made mine a big block; this will be a fist. You may also have noticed that I stretched the torso down a little bit.
Now for the crotch. Click on "Polygon" at the top of the screen, then click "Points" to highlight it. Click at around -5cm on the X axis and -1.5m on the Y axis (in the face view) and 0 on the Z axis (in the side or top views). Now click "Make". Make another point with the same Y and Z settings, at 5cm along the X axis. Now create a polygon out of these points, and the two points in the middle of the chest. Make another polygon out of the two new points and and the two points on the back. Then make a polygon out of each side of our dandy little crotch. Take a look at the pic if you're confused.
Now select the polygons (should be 2) on one side of the crotch, and merge them. Do the same to the other side. Now, select both of these two polygons and extrude them. These will eventually be the legs, just in case you havn't geussed that already.
Now, see those little squares at the top of the screen, between the Quit button and the Display button? And you see how one of them is yellow with a black dot? That's the layer you're in right now. Click on one of the empty squares (on the top row, not the bottom row). This is where we're gonna make our head. Start with a simple cube. Now we're gonna add a point. Add a point at 60 cm along the Y axis, and 0 along X and Z. Now delete the polygon on the top of the cube. Then, make a polygon with the point we just created, and two points on the top of the cube. You should make a total of four polygons, and his head should look like a pyramid.
Now move the bottom two points on the back of the head closer to the front. About -20cm along the Z axis should do the trick. Now we're gonna add two more points. Add one at 50 cm along the X and Z axis, and -30 cm along the Y axis. Then another one with the same coordinates, except -50 cm on the X axis. Now delte the polygon on the back of the head; we're gonna make a new back for his head with the two points we just made. Select three of the points in the back of the head and make a polygon. Now select another three and make another polygon so that there is a flat square for the back of our monster's head.
Now you may have noticed that the sides of his head in the back do not exist. This would look pretty stupid in Quake. Create two new polygons, one on each side of his head. That looks a lot better. Now move some of the points around a bit if you like, to give it a more realistic look (well about as realistic as you can get with so few poly's). I made his face get narrower at the chin, and raised the back of his skull a little.
If you look at the bottom of the head in your preview, you'll notice the hole there. Create a polygon to fill this hole, then extrude that polygon to make the neck. As always, don't forget to delete the polygon you extruded and merge the extra points. Delete the bottom polygon of the neck, and you're basically done with the head. You may want to move some of the points around a bit so the neck doesn't look like a cube.
Now, remember those funny little layer buttons at the top of the screen? Well, here's where they really come in handy. You may notice that now you have a grey button with a black dot in it, and a yellow button with a black dot in it. The yellow button is the foreground layer. This is where our head is. The other one is one of the background layers; this is where the rest of the body is. To let us see that background layer, we have to click the grey button underneath the grey button with the black dot. The body should be shown as a black wireframe.
By now you may have noticed that the head is a bit too big. Click on "Modify" then "Size" and shrink it down a bit. Make sure none of the head is touching the body. Now click on "Tools" and click "Boolean". Click "Add" and then click ok. Now grab all the points on the head and position it how you want it.
And that's it for this tutorial. I know I didn't finish the legs, that's up to you. The point of this tutorial is to teach you how to make your own models. You not always going to have someone to tell you how to do it. I've given you enough of a start on the legs that you should be able to finish the model just fine on your own. Play around with the model, try different ways of accomplishing things, see what works and what doesn't work. Remember, when you finish the model, be sure to triple the surface or else it won't work in Quake. Good luck.
Just in case you were wondering, this is how my model turned out. I moved the verticies around to make it look less human. You may notice the position his arms and legs are in; this position makes it easier to use Bones on it to animate the model.