I agree with Dragonchilde - it is about tracking changes over time, not about your 'true' weight. So trying to achieve the same conditions each time will allow the best comparison over time.
I'd recommend in the morning before breakfast but after you pee, with as a few clothes as modesty will allow. Not because this produces the "lowest" weight, but rather that it strips out as many variable factors as possible. (And even then, your weight can fluctuate by several pounds from day to day, due mainly to changes in your hydration levels.)
I'd also add measuring yourself with the tape as a better way to track progress over time than relying solely on the scale.
The reasonable man adapts himself to the world; the unreasonable one persists in trying to adapt the world to himself. Therefore all progress depends on the unreasonable man.
| current weight: 178.0