Hey Rod,
I don't usually draw spline placement, since I don't necessarily stick to my sketch (or my photo reference), and in this case, I only drew a side roto, and even that was only for the head and torso. I wing the rest, especially with creature type characters where you don't have to get proportion 100% right on (a lot more fudge factor than you have with human characters). I come from the extrusion school of splining (and modeling in general my technique is pretty much the same in wings and LW, with just a few different rules to follow). I start with an eye model, position and size it and then do a ring for the beginning of the lids, shape and extrude, shape and extrude, until I get to the point where I'm at the nose bridge. Then I do the same thing with the mouth (just half of it though) then connect the two sections up and hen work in the nose, get the general face the way I like it, extrude out the back of the head and under the jaw until they join to shape the neck, more extruding... you get the picture... didn't mean for this to turn into a modeling tut, but this is true for anything I make, whether it be a minotaur, a goblin or a voluptuous salty pirate babe ;-).
Which brings me to your other question. I model only half... because I'm lazy. I do copy flips along the way to check proportion but its just too much work to make sure mirror mode is on, or off depending on what I'm doing, and my technique developed before that was available so it falls into the "if it ain't broke, don't fix it" category. I get everything the way I like it, do a final copy flip attach at the end and then do little tweaks to throw the symmetry off a little.
Boy that was long winded...
-Matt