Matt Haughey shares some of his favorite weight loss advice for geeks. The moving average advice is particularly useful.
There are many explanations of why one would use a moving average, but I'll just say that it covers your weight trends and lessens the daily fluctuations. This means if you drop 0.1 pounds every day for a week then one morning you weigh in at one full pound heavier than the previous day, your entire week wasn't shot that morning because you'd still be trending downwards. If you stick to your plans you'll often see weight continue to go down even with the occasional hiccup.
Two things of which you should not fret the daily movement: the stock market and your weight.