I weigh in once a week. It helps me to stay accountable. It can also be discouraging and make me
so sometimes its hard.
It depends on the person. If, like me, you have a love/hate relationship with the scale I would suggest maybe every other week or maybe even once a week. This will help you to see what is working and what isn't, but I wouldn't go a month between weigh ins. It didn't work for me.
But it's really up to you. You have to learn what works for you.
I hope that helps.