I always play the game for about 8 or so hours, get a feel for how leveling and character building work, and then start over and go through the whole game. This has worked for me through Morrowind, Oblivion, Fallout 3 and New Vegas, so I will do the same for Skyrim.
This. I usually make a character or two, try out some different options in the beginning part and then make a save before the "final customization" part. Hopefully Skyrim will have the option to finalize your decisions, and completely remake the character after you finish the "training" section.
This is usually when i decide exactly what i want my character to look like, which honestly is the only thing that matters that early on in skyrim, since classes and birthsigns are out the window.