Definitely don't weigh yourself more than once a week, if you're focused on getting the number down. It's going to go up and down, and just like you said, the fluctuations will drive you insane. Pick a day and make that your 'weigh-in' day (preferably at the end of the week, after you've gotten all your exercise in). Weigh in as soon as you wake up from a good sleep, and all you'll see from the scale is the work you put in that week. I used to make my weigh-in day the same day as my 'cheat day', to reward myself for the work, and to put as much distance as possible between 'cheat day' and weigh-in day (it gave me more time to work off whatever cheat meals I ate- haha).
Best of luck!