I could find that different texts follow different steps in the conversion of CFG to Chomsky Normal Form. I couldn't find any presumptions they made in the conversion steps. I have some questions regarding the conversion.
Most text books tell us about only two rules $A \rightarrow BC$ and $A \rightarrow a$. But some texts say that starting productions should not be in the right hand side. Why some stress on that rule and others not?
When talking about the rules some don't stress much on the condition of removing useless symbols. Is this condition mandatory or not?
Which is the best rule? Remove useless production, remove $\epsilon$ production, remove unit production, adjust the resulting productions so as to reflect the CNF rules.
Converting a grammar to Greibach normal form requires first converting the productions to Chomsky Normal Form?