there simple point to check wether the grammar is regular or not
first point . If given grammar contain two or more than two non terminal in the right hand side of production than the grammar will not regular grammar
second point. a regular language can have more than one grammar which can be regular or not regular
take an example of regular language (a+b)(a+b)+
and grammar
S->AA
A->aA | bA | a | b
here the language is regular but the grammar is not regular
but you can generate at least one regular grammar for this language
conclusion we can generate at least one regular grammar for every regular language
third point . If grammar has production which is either left linear or right linear but not both the the grammar is a regular grammar