Although there are more measurements that can be taken and used, below are the 5 main ones I use with all my clients that provide enough adequate data for measuring & tracking progress. 

• Chest - standing, and measured with a breath out just above the nipple all the way around and under the arms.
• Arm - with arm hanging to your side - measure half way down your upper arm below the shoulder (find widest point). Do one or both and remain consistent with future readings.
• Waist - all the way around your stomach, just above the belly button
• Hips - all the way around the largest point around your butt
• Thigh - standing & measured around the largest part of your upper leg

As with the scale weight, I always suggest measuring in the morning when you wake up, before you consume anything, and ideally after you've gone to the toilet. Ideally, do it yourself rather than relying on a partner, as you are the only person that will ALWAYS be with you. Two different people measuring with the same tape will more than likely get a slightly different results

Frequency of measurements depend on your timeline & your goals, however I generally have clients take their measurements every two weeks. If you want to do it weekly then by all means do so.

 To ensure accuracy & consistency:

• Use myotape or another similar brand (pictured below)
• Take measurements in an non-flexed state 
• Stand up straight
• Pull the tape tight, keeping pressure against (but not pinching) the skin & ensure the tape is kept level and not angled
• Take measurements in front of a mirror for better visibility
• Always measure on bare skin and never over clothing