One thing I've done is to pick out a specific outfit to wear each week as I weigh in. Behold:
It's a stretchy & thin leopard shirt paired with black pants. I take off my shoes for weigh in.
If you weigh the same thing each week, you know the score right away. Sometimes when I wore different clothes in the past, I would start justifying the weight in ways that were not good.
"I'm weighing jeans...that must count for a few extra pounds, right?"
"These sneakers add 2 pounds by themselves."
"Oh it's ok, it's really just this sweater"
It's true that clothes can add on some weight, but not THAT much. When I wear this outfit, I know this week's poundage is compared to the same parameters as last week.
It doesn't matter what your weigh in outfit is. You can have no clothes (though I don't think places like Weight Watchers would appreciate you showing up like that ;) ) or be decked out in heavy snow gear as long as it's the same weekly.
What do you wear to weigh in?