Symmetry is usually greyed out for me so I don't know what conditions need to be present for it to work. Mirroring joined would be for the head and mirroring separated would be for doing ears sort of thing. You can right click on the object panel for quick access.

create line - first click creates a vert, second creates another vert and the line joining them, and so on.
create tri -  3 clicks and you get a tri
creare face - 4 clicks creates a poly
It tends to be a labourious way of modelling so I tend to use it for joining parts of primitives together (bridge I believe its called in wings)

Without a screenshot I'm not sure on your last point. Mesh smoothing will just subdived the polys and doesn't take into account any curvature (catmull-clark sub-d will but you'll need a different style of modelling).
You should be able to select any vert or line or face and muliples of (shift select) I'll post ascreenshot if you're having trouble.

cheers
Mark