I've decided it so much easier to shave while in the shower than after. I'm sure I go through more hot water this way, but it works better.
When I first shaved my head, I used the sink--second time was in the shower and whoo-boy is that definitely the way to go.
I shave daily, because I can keep it smooth after just one pass--if I skip a day, it takes me about 15 minutes to shave it twice...once with the grain and one against.
It definitely works better--keeps the hair softer and the pores open due to the heat and steam. I've shaved at a sink a few times since, and each time I nick around my ears, which is weird since at the sink I'm using the mirror and in the shower I rely totally on touch to make sure it's smooth.