I weigh every morning and night...only counting the morning weigh ins though. I find that I can fluctuate 2-3 lbs per day. It is discouraging sometimes, but I would rather know that it is a daily fluctuation than weigh once a week and be really disappointed.
I weigh every morning (pee, strip, weigh) but only track once a week. I like to see the fluctuations, but only base my total weight loss on what I see on Friday morning. I find this keeps me motivated the best.