Some "weight loss authorities" suggest weighing yourself only once a week because body weight can fluctuate, therefore making daily weigh-ins futile. BUT THIS IS NOT TRUE!! Weighing yourself daily, along with monitoring of your calories and activity levels are critical to establishing lifelong weight management habits. Taking a daily weigh really helps you keep on track. Remember it only takes 1 day to gain body fat. Why wait a whole week to measure it? Weight loss is a day-by-day process. The earlier you see your weight going off track, the faster you can start get back on track!
Be sure to get a high quality scale, preferably one that will give your weight to at least a 1/4 of a pound. Then weigh yourself daily. Take your weight first thing in the morning at the same time each day. Be sure to wear the same amount (or lack of) clothes. Then write down your weight in your journal. This will help you!
I have taken this one step further and have been tracking my weight loss in a spreadsheet. My weight does spike some days but that's mainly due to fluid retention. Those pounds are quickly lost.