I do 'girth' measurements once a week, when I weigh in Sat morning before I eat/drink/pee/etc.
Or just when I remember to do it, some weeks.....
Common areas to measure would be:
Upper arms - widest part
Shoulders - widest part
Bust/chest - I do this lying down with no bra, to try and keep things consistent/unaffected by my 'support' for the day
But most people just measure normally.
Waist (there are a few places: halfway between your ribs + hips, at your belly button, or at the smallest part of your middle - that's what I do, since it's my 'natural' waist)
Hips - at the bones AND/OR
Backside - widest part of your a$$/hips/middle lower body
Thigh - I usually just go for the widest again
Others you could think about
:
Neck
Wide Waist - my personal problem area, which is why I measure the widest bit of my tummy
Lower arm - widest part below your elbow
Knee - widest part above the joint
Calf - widest part below the knee
I also just use a sewing tape measure, and I don't stress too much about them - I'm pretty lazy with my measuring, I just get an idea of 'did I go up or down?' and 'by a lot or a little?'. Have fun!