How can i export a 3d model in game?
So where should i start now...
If you haven't written any 3D apps, then before you decide on a 3D modeling program, I'd suggest you learn the basics first:
1. Choose a language, IDE and platform for development.
2. Get a very simple program coded, compiled and running - perhaps rendering a box (which you create yourself), then a spinning box, then a spinning box with an eyepoint (camera) that you can move around.
Step 2 will provide you with experience in setting up a 3D rendering pipeline, learning about winding order, front- and back-face culling, etc., and require you have a good understanding of the math for vectors and matrices.
After you're comfortable with the basics of working in 3D, then think about more complicated models.
EDIT:
how can i export a 3d model in my game
Just to get some semantics straight, you likely mean import a model into your app. If so, importing model data to render it requires you have an understanding of how you're going to render it - for example, the structure of vertex and index buffers. That's the reason I suggest you understand rendering in 3D before you complicate things by trying to code an importer.
Is there any book that'll help me in learning 3d modelling for games?
Maybe. Googling for "3d game modeling" yields over 4 million hits. Amazon.com alone has 233 hits.
What Buckeye said....
additionally you might want to read the primer for beginners: http://www.gamedev.net/page/reference/faq.php/_/for-beginners-r1
depending on wheter you want to learn to program a game from scratch, or you want to dive in headfirst into 3D Game dev, you should follow Buckeyes advice which is very good for a bottom up approach, or have a look at some existing Game Engines: Unity, Unreal 4, and tons of others (see devmaster.net, they have an engine database where you can search for engines).
These Engines will have the import problem already solved for you, as long as you don't use a very rare, exotic format (.obj, .fbx, and sometimes the blender format should be ok).
Of course using an engine will not save you from learning some of the basic stuff in the long run... you can jump in and have some nice objects moving around quicker, but if you don't catch up to what others learn while creating their engine from scratch, you will hit a wall at some point.
Then, while Wings3D certainly is a fine 3D Package (used it myself for a short while), generally people use Blender as THE free 3D Modelling app. The interface is not as intuitive as other 3D Applications, but Blender will give you the most complete and powerful 3D PAckage in its price category (Which is 0$ :p ).
Of course, if you are here because you want to learn how to write an importer for your very own game engine, feel free to disregard my comments :)
Is there any book that'll help me in learning 3d modelling for games?
What are you looking for? There are books on modelling static level objects, special books on creating 3D Characters, books just on animating them, books on modelling vehicles (which comes then close to CAD (which is used for example by the automobile industry))...
3D Modelling is a very vast topic to cover. If you are looking for GOOD books, you need to be much more specific.
For starters, I would search on youtube (tons of videos on modelling), and I would search the resource and download section of the 3D Program of your choice for tutorials (Blender must have a million tutorials, some of them are even pretty good).
Little word of advice: don't start with trying to model a realistic human model. You will waste months without finishing your project. Start small, with a rock, a Table, a chair.
Something that is simple to model, can look good with very simple textures and does not move.
Start with simple polygon objects without normalmaps (normalmaps are 2D Images that make the object look like it would have more bumps and crevices than its polygon count allows). Then, when you feel comfortable with Polygonmodelling, try some texturing (applying a 2D Image unto the model that will define the colors).
If you got that right, you can move on to sculpting (which is normally used to create an even higher polygon model, which then is used to create a normal map for the low poly object).
I wouldn't get into Animation until you have learned all that. Animation is a HUGE topic of its own, there is a reason why in big studios and films, they have separate people just handling animations (and sometimes people just PREPARING the models for the animators (which is called rigging))
