I first create really rough charcter then I delete half of the character, use the snap option and duplicate that half with instance option enabled.
After I'm satisfied I delete half of char, use sanp option again and then I use duplicate geometry under the Polygons menu.
That's the easiest way to do it for me.
However if you are working with subdivision surfaces you should convert them to polygons to use technique(s) explained above!
If the worst hasn't happened yet, that's because you haven't tried everything yet!