Choosing your tools: Blender 3D
All right, before we get started, I want to make something perfectly clear: Blender is not the best tool for working in 3D. It's hard to learn, has a clunky interface, and generally takes an extended time learning how to use it properly.
And so does every other 3D development tool out there, including Lightwave, Maya, 3dMax, 3dCoat, and Zbrush. If I didn't mention a tool, then assume it's hard to use too.
Generally, the thing to keep in mind is to choose a 3d platform and stick with it. While the cost of the software is a factor, there is a second cost that people always miss: The personal cost in time and effort to learn their chosen software. Software does not run itself. You will have to learn how to use it, and that takes months, if not years, or practice. If you spend a month trying to learn Maya, and then switch to 3dMax because you think it's "better" in some way, then you are going to lose a lot of the useful experience you gained in Maya and have to start over in a lot of your training.
So pick a tool and stick with it.
Myself? I use Blender 3D. Here are my list of reasons:
Personal Investment: I started with blender in the late 1990s, and have been using it for two decades now. Switching to another platform would slow down my productivity to a crawl as I relearned how to do even the most basic task.
Evolving toolset: Blender is opensource and evolving. Every few months, I get a new tool to add to my library built into an interface I am already familiar with.
Swiss Army Knife: One of the things that make blender so hard to use for newcomers is due to how many features it has. It not only deals with 3D modeling, but a huge number of other tools. It can even be used as an advanced video editor, and even allows camera tracking (tracking a film camera's position in 3d space) for visual effects.
Works with Unity: If nothing else, the FBX exports from blender work in Unity with minimal Pipeline tweaking and effort.
As you can see, my reasons for using blender probably not the reasons you would use it. Most people would mention it being free, for example. Well, as we know, nothing is free. While Blender may not cost you money directly, it and other 3d software will cost you a huge investment in time to learn them.
So, this article is about blender. If you do chose to start learning it, I advise the following:
Go to https://cgcookie.com/course/blender-basics and use those basic videos to learn how to navigate blender.
After those basic tutorials, check out other training videos on that site. There are months of videos for you to learn from.
That will get you started. Next, many will ask how to use Blender 3d for game development. Learn the needs of game modeling. It is TOTALLY different from artistic modeling. Polycount and design methods don't matter nearly as much when you are rendering a character inside blender, as opposed to when you are building a model to be displayed in real time inside of Unity3d.
While you can build the source model as high resolution as you like, be prepared to have to build a new model for the game based on your highres model. The normal way to do this is retopology. This is the art of making a new, simpler mesh that generally matches the form of the highres mesh. All the detail is then rendered into textures.
Get used to working with UV maps. Learn how to use them well. Knowing how to use UV maps to texture a model is absolutely vital to game model design.
Normal and specular maps. Learn em. Game engines tend to use the holy trinity of Diffuse (color), Specular (shine), and Normal (surface angle, NOT BUMP) maps. Don't just use them blind: Learn how they work.
Learn how to optimize the mesh by hand. Where you may need to add extra faces or edgeloops (look it up), and why. Game models can be rendered utterly useless by bad topology. This is one of my main issues with 3dMax: Artists getting used to using the automatic stack tools that make modeling easy, but don't even know how to clean up a mangled section of mesh that has a hundred triangles the size of a pinhole that messes up the model in unity.
Again, one thing to remember about 3d development tools: Use what you want, and stick to it. Switching tools won't help you to learn faster.