The tape measure should be just snug. Not tight enough to compress you at all, not loose enough to get a finger under. Typically when doing measurements I measure waist, bust (easier with a bra on, really), hips at the widest point, upper arm, and upper thigh. There's more measurements you can take, but those should give you a good picture of what's going on.
Hello there, Clarrie! I just wanted to give you a quick hello , and to say that it's such a pleasure to see you around here as well. I really enjoy your blog, and I think you're doing just beautifully. You seem like a lovely person; if ever you need help with anything or would like an ear, please don't hesitate to let me know! Best to you....and keep on enjoying those buggy walks with your dear son.