These are some useful tips that you can us while weighing yourself..

• Weigh yourself with clothes on, after dinner...as well as in
  the morning, without clothes, before breakfast, because it's nice to see
  how much weight you've lost overnight.
• Never weigh yourself with wet hair.
• Always use the toilet first.
• Weigh yourself after a haircut, this is good for at least half
  a pound of hair (hopefully).
• Exhale with all your might BEFORE stepping onto the scale (air
  has to weigh something, right?).