Mirror Modifier
The mirror modifier can really speed your work flow if your creating something that is symetrical for the most part. Examples of this could be vehicles, character bodies and heads as well as various consumer products.


Mirrors use is pretty simple. Simply select the mesh you wish to mirror and apply the modifier along the desired axis. You then press copy to duplicate the meshs mirror equivelant.
The final processes are to collapse the modifier stack and then weld the vertices down the seam where the mirror copy meets the original mesh.
