Hi Shelley - to get an accurate reading you need to take measurements with skinfold calipers (it's a difficult calculation, but not impossible). You take a measurement of your tricep, hip, and shoulder blade. Some people do thigh, too, I think. I've had mine done at the gym and had to do my own in Year 12 PE.
My scales have a body fat and water% reading too. while I don't think it's 100% accurate, I just use it as a guide.
SarahC has her own calipers and takes measurements weekly, so she knows a lot more about this stuff than I do
Just keep moving! And don't be lazy...
SW: 74.3kg - 1/1/09
CW: 71.1kg - 3/5/09