Instructor started me with 12 lbs and was very reluctant to give me more. But I am a lardass and float like a cork in warm saltwater. Just could not get down with a dumped BC and empty lungs while kicking.
I've been instructing a few years now... and we try to get the weighting right first time in the pool:- here are a few issues we come across
1. People get anxious about sinking so they super fill their lungs. We try to get them to relax
2. People complain... "I can't sink!" yet they are flapping their feet. We try to get them to relax
3. When at the surface, doing the buoyancy check, people who's weight we've thought we got about right, when they practice find that they're usually a kg or so over weighted. We tell them to remove a weight, and get them to relax.
I was super weighted to get me to sink in my open water. 3mm shortie with 10kgs of weight according to my log book. Fortunately an instructor at another school was able to advise me and I halved that over night. Now in a 3mm long suit I can get away with 3kg (steel tanks). Although I got quite a shock on a visit to the Red Sea, with a 6.5mm semidry and aluminium tanks!
I think generally as new divers we have to practice... and see if we can drop some weight at the end of a dive. Oh yer. and relax