For me it varies. Early on I wieghed myself everyday, mostly because it helped me see that fluctuations in weight were normal.
Now I weigh once a week and that works fine. I may even decrease it. The bottom line is to weigh yourself so you can keep track if you want, but not to let it make you crazy (scale-insanity is a common affliction for any dieter

).
I also measure once a month. Any sooner than that and there isn't a very big difference. I also take pictures when I measure and pair them with the measurements so I can see how I look as I shrink.
Hope that helped a bit. Good luck!
