Weighing yourself in the morning, after the whizz, will give you more consistent results (it will be your lightest weight, but it will *always* be your lightest weight). Even that will fluctuate daily, but it's less likely to include the pound of vegetables you had for dinner etc. Even better is to plot these daily numbers on a graph, and then you can more easily see the pattern over time. That is if you are fixated on weight, though.
I still really enjoy the hardcore numerical approach to anything related to the body, though. My husband and I needed to lose some weight, and we went on a totally anal calorie counting plan (I printed out lists of the stuff we eat, in /100g units, and kept it in a binder on the table, and we weighed everything significant on an accurate digital scale). We both ended up losing 20 lbs, but the nice thing was that it had to work. I've been eating fairly healthy for a long time, and getting moderate and sometimes heavy exercise (usually walking at least 3 miles a day, often more intense cardio and weights too), but it wasn't enough and so I found the 'just eat healthy and exercise' advice pretty frustrating. The problem seemed to be that I was eating too much, but I never for certain that that was the specific problem until we actually kept track of it. In the end I'm glad I did it if only because now I know that I actually do have control over this process if I choose to exercise it.