First, you must be comfortable working in a 3D authoring enviorment. Working with programs such as 3D Studio Max, Rihno, and Nendo, etc. will give you the power you need to create 3D objects and enviorments. Working with these applications will give you the ability to create complex 3D objects.
Now, when you bring these objects into a program such as Swift3D in 3DS format, you can manipulate your objects and animations you made in the 3D program. Something very important though, when working in Swift3D it is very important to keep in mind the matter of the final SWF file size. I feel this is one of the most important matters to take into consideration when it comes to 3D and Flash. Swift3D and Flash are tools. Tools we use to create the final product. I feel that a top of the line 3D guy would know when to use which feature with which tool at the appropiate time. For example: If you have a 3D object that flies away from the camera, you could export the entire animation from Swift3D and import all the keyframes into Flash. But you could get the same effect by exporting only the first frame frome Swift3D and in Flash use a motion tween that scaled down the size of the image between two keyframes. The effect is exactly the same, but the file size with the motion tween is a lot smaller.
So overall, the top 3D guy would be comfortable making 3D files and then knowledgeable enough with his tools to optimize the animations while keeping the inital desired effect.
The only thing that I would add to what Alex has said is knowing how objects behave in the real world environment. Speed, Gravity, lighting, etc. Motion as a whole. This falls more into design and animation but is an essential part of 3D. I would also say you need to know how to model your own stuff. Using pre exsisting models may do for now. But not long from now everyone will have the same tv, chicken, pig, house etc. Hence the "webesk" look I said 3D could take on like the animated gifs of just a few years ago. Want to be top shelf, do your own stuff. Those are my opinions on the matter. Regards, Bill
In the beginning the web was without shape and color, and the hype covered the darkness of the net. Then there was a Flash and life came to the web and vision became reality.
if anyone else has any ideas... or perhaps would like to break down the skills that make up a good 3d modeler.. I'd apreciate it.. (or I'll have to hit local college callenders for course descriptions!)