I agree with Brown. I always weigh butt naked right after I get up and pee. Then I jump right in the shower.
You always want to weigh in a consistent manner also. If you wore underwear the first time. Always wear underwear. Otherwise you will bug yourself the one day you don't weigh yourself in your underwear.
Naked as possible - I even take any hair ties out LOL Always after peeing, and after I have been up for a few hours without eating. I only do my "official" weigh-in once a week.