I tried to do the once a week weigh-ins and I couldn't handle it. I was too much of a nervous wreck to find out what happened over that *long, long* week. So I started weighing every day first thing in the morning before I eat or drink anything. I haven't experienced any weight fluctuation this way, other than when it's due to hormones (even then, it only shows up as 1 lbs up). I like to weigh every day because then nothing can "sneak up on me". It's more psychological than anything else. I don't like surprises.