I agree with Nat. Find a good scale and use it wisely. I use a TANITA brand scale with BF% and it has been excellent in consistant weight measurement.

I suggest something that is not often recommended and that is daily weighing. HOWEVER...I do it twice a day. When I first rise and just before I retire for the night. I record both the weight and BF% for these times and feed it to a spreadsheet that does a 7 day average of this data. This helps minimize over reacting to either the normal daily weight and/or BF% variations that will be seen.

Understand that BF% reading can vary wildly. Factors like hydration, muscle activity, bladder/bowl contents, and recentcy of major exercise can have huge impacts on readings and will drive you wild unless you understand that. Thus, again, I rely on 7 day averaging. BF% are typically highest in the morning (most dehydrated) and lowest in the evening.

I have done this routine for 2 years and feel very confident in how it works to avoid over-reactions to daily weight fluctuations. YMMV.