One thing that you have to take into consideration when modeling for games, is texture space. You have a limited amount of space for your textures so you have to be as conservative as possible. Of course, this isn't something you have to worry about at all if you're modeling and texturing just for render or for movies.
Because of the concern for texture space, things that are symmetrical are usually only textured for half of it, and the other half is flipped and overlayed with the first half. Faces are one of the things that are usually cut in half since a face is usually symetrical down the center.
Of course if you want to do something like have a scar on one side, or put little stars over one eye or whatever, then you'll need to keep the whole thing laid out and texture both sides of the face as a whole.
If you have plans for your face to have some asymetrical aspects to it, you may want to keep it as a whole unit, other wise you'll want to do what I"m about to do for the neck. The neck os definetly going to be mirrored as I see absolutely no reason to keep it whole, so I'm going to flip it right off. First select half of the neck, right down the center. We need to break these UVs off before we can flit it, so press Ctrl+D to detatch them at the seam. Next go to Tools > Flip Horizontal, and move it overtop of the other side so that tey line up. Select the whole thing and Ctrl+W to weld the two sides together |
