I used to weigh every day. I figure it gives me a better idea of my fluctuations, so I know what's "normal" for me. I always figure, what if I weigh weekly and one Friday is my "real" weight & the next Friday I'm retaining 5 lbs of water? Not an accurate picture of how my week went, in my opinion.
Now, however, I don't weigh myself. I lost 35 lbs last winter (yay!) and over the summer gained about 10 back (I cook at a fly-in fishing lodge in the summer, and while the food is healthy, a lot of it is also rich; I don't worry about it too much while I'm up there). Anyway, I gained the weight & rather than bring myself down with numbers - I can certainly tell my pants are too tight - I just started doing what I did last winter - counting calories & doing a lot of exercise. I know it works from last winter's results (and from my pants now, thank goodness), so the scale is gathering dust. Probably when all the size 10s that I bought in May fit perfectly again I'll hop back on.
I used to weigh once a week, then I hit the plateau from ****, and the scales were seriously doing my head in, so I decided the best thing to do was ditch the scales. I have my measurements and body fat taken every eight weeks, so that is what I rely on mainly. However I have taken to weighing once a month, and I do this at our local drugstore on a scale that does a print out. And if it's a good result, I can go and buy a lipgloss or an eyeshadow, and if it's not good, I just go home!
I weigh in everyday(unless I forget) But Saturday is my official weigh in. I like seeing the fluctuations so I can tell wether I ate too much or it is just water weight. It can stress you out if you take it too seriously.