whatshouldiuse,
First of all, we have only read newspaper reports of an accident in a highly specialised industry. For any particular incident the accident investigation report will be closer to the truth, however, in general terms - to say "I do not want to go overweight" is not good enough.
An aircraft commander has a great deal of authority and, within reason and the law, may run the flight exactly as wished including throwing off luggage or passengers which take the aircraft overweight.
Unfortunately some operators demand illegal operation from low hours pilots who do not wish to be fired or to whistle blow. This, of course, also puts compliant operators at a commercial disadvantage.
I was told by a flight ops inspector that it is very difficult to monitor these breaches of the law due to shortage of staff and, in any case, when a FOI turns up, the jungle drums beat, word gets around and the 'goodfellas' operate legally until he's gone.