Share 'How do I know which seeds can be saved?'

Hi folks, Heres a question that im sure you can answer: How do I know which seeds can be sown and grown for purpose of seed saving? I usually only sow seeds from organic, heirloom suppliers - I have no problems using the seed from these for the following year. Question: can I seed save using plants grown from commercial seed  - i.e. yates,  kings seeds etc? (In other words - are the commercial gu…