You need rather powerful computer to do modeling. My computer is barely enough for my purposes. It can do simple renderings rather quickly, but with lots of objects, transparent shadows, reflections and such, it takes ages (2 minutes?)! And I'm talking about a single picture now, you can imagine how long it would take to render a full-length movie with all the effects (simple math?).
What is 3D modeling?
You know it, silly! It's about creating models using different kind of 3-dimensional shapes or something. I'm not a teacher, so I'm not going to explain it too much. These models can then be used in different way, like rendering a single picture or using them in a game or animation.
The program I use mainly use for 3D modeling is 3D Studio Max 7 (3dsmax as short). I've tried few free ones too, like Blender, Sketchup, landscape renderer called Terragen and some others I don't remember right now. I like the interface of 3dsmax, because it's rather logical, customizable and fast to use. It's kinda hard to switch over to another program and to learn another different interface. I'm having this problem when I want to do something with Blender! This is why I'm going to talk about 3dsmax.
On the right you will see the default interface of 3dsmax (well, different color scheme). On the top is the toolbar and on the right is the command panel. The big main area in the middle is for the actual modeling. It's divided into four sections: three for each direction and one perspective view.
The toolbar buttons are customizable for your own needs. I keep there buttons I need the most, like move, scale, rotate and mirroring object buttons and different kind of rendering buttons and maybe something I don't use very much.
The command panel has different kind of tabs. "Create" tab contains subcategories for objects, shapes, cameras, systems etc. Every subcategory also contains another subcategory list for different kind of objects, shapes etc. And those subcategories contain different buttons for the actual objects, shapes etc. "Modify" tab contains stuff for editing the object properties and adding modifiers. Rest of the tabs are "hierarchy", "motion", "system" and something I don't remember now (I don't uset these tabs often anyway).
How to do the modeling
I'm going to show how to get started with 3dsmax. In this program (like usually in most of the 3D modeling programs) you can start the work by using basic shapes. Modifying and joining the shapes and objects together creates the actual model.
Here I placed a box in the scene first having "Create" tab open on the command panel, selecting the "Box" button and placing it on the scene. After this you can modify the object properties, add modifiers, change colors etc.
3dsmax has this big list of modifiers (part of the list on the right). Using these modifiers is the main way to edit objects in 3dsmax and they give you the ability to create almost anything from a simple shape.
You can also download plugins to get more. I, for example, used Greeble in this picture. It gives the surface a blocky/city style. Actually the whole scene consists only of one object with Greeble and three lights (yes, I'm a pro).
Here you can see how to start shaping somekind of a robot foot only combining boxes and two modifiers called "skew" and "taper".
Modifying multiple objects at the same time is easy when copying an instance of the object. Then all the instances share the same properties and modifier stuff. Reference copy is almost the same thing, but it shares only the modifiers that are included in the time of copy. This is especially useful in large scenes with big amount of same type of objects.
In the picture below you can see this mech foot I've done (which is part of my latest robo-thing, delayed of course). It fully made of basic shapes and using only few modifiers. Adding more and more little shapes here and there gives a nice detailed look. One thing I've learned: viewers don't see all the details, but they will notice when there are no details at all.
What else you need to know about
I didn't include everything about 3D-modeling in this post and here's few things you should consider when you can create basic models (even basic models will look pro then).
One of the most important thing in making objects to look realistic and cool is what kind of material the object has. Gray, non-glowing object doesn't look rather nice, does it? When you give it some glow, reflection (maybe with distance-blur), some bump-mapping and so on, even a simple object can look awesome. 3dsmax also has this materal called "Ink 'n Paint", which gives the object a cartoony look like in this picture.
Lighting and effects
One sure thing to make your images look cool is using well both lights and effects. Like in photographing, you can emphasize scenes by using correctly targeted lights and using different kind of light types and effects.
Polygon based editing
If you want to make models for games and have even more detailed objects, polygon editing basicly the only way (if we don't count in NURBS or something similar). In 3dsmax you can start with basic objects, shape them with modifiers and then convert them to polygons, and even after it you can put more modifiers etc.
Well, this type of modeling is easier for beginners and fast for rendering purposes, but not good if you want to use your models in games or animations. Then you should rather study how to model objects in polygon level, booleans, optimizing, skinning, skeletal systems and so on.
Be sure to check out my 3D models for more examples.
Damn this post took long to create (and you noticed how much I use brackets?). Next time I could talk about photo editing, programs for that and maybe about some nice effects and stuff. Be sure to vote what you want me to mumble about (or make me shut up?).