Let's create 3d logo for some 'company'.
2. Select logo ( or whatever this is, but imagine it's a logo ),
and put some lighter color, like blue ( for easier rendering, or to see what's rendering ).

3. Then while selected, go to Effects >> 3d >> Extrude & Bevel

4. Click OK, and while object is selected ( logo ), go to Object >> Expand Appearance
5. Okie, we expanded it now, but it's still in one group, so we have to ( while selected -.- ) go to Object >> Ungroup
Or you can select object and press Shift + Ctrl + G few times, that will ungroup it also.
6. Next step, it's ungrouped and we can select any parts of it.
7. Lets create some gradient, like this

8. Apply gradient to every section, surface, bevel etc

9. And final looks like this

After more playing, here is result

Source: http://pstnt.blogspot.com/




