If you want to see real changes in the measurements it's best to do it monthly. At the outset you'll be losing fat faster and inches faster so every 2 weeks wouldnt be too short a time, but eventually that will slow down - a month gives you enough time that you'll actually see more of a change.

Be sure to measure in many places. Neck, bust, under bust, waist, belly button, hips, wrist, upper arm (both of them), thighs (both of them) and calves (both of them!). Often you'll not see a change in one side of your body but there will be a loss on the other - fat moves around! You'd be surprized at how much you can lose off your wrist, Dee

Nat