I weigh every morning when I get up and my weight is, typically, within a pound or two every day. You should try to weigh at about the same time every day - after first getting up, before eating/drinking anything, but after going to the bathroom and in the same type of clothing.
You do have to keep in mind that weight can fluctuate a lot, depending on what you ate the day before, how much you drank, how much you went to the bathroom, etc...For instance, if I eat a bunch of salty things in the evening, like popcorn, chips or nuts, I know I will retain fluid and may weigh as much as 5 lbs more the next morning. I also know that if I exercised more and didn't eat as much, I might a couple lbs less.
I don't worry if my weight is fluctuating; it's when it rises 2-3 lbs and won't come down over a period of days, that I realize I've actually gained and that I need to take action right away to lose it before I gain more. If it's down, consistently, a couple or few days in a row, I'm confident that I lost that many lbs.
Many people find it's better to weigh only once/week. You have to find what works best for you. It's "not" a good thing to weigh more than once/day, because you'll almost always weigh more during one part of the day than you will another.
Best way that I've found is once weekly, in the AM.