You must look at the pattern of rhymes. For example
Monday's child is fair of face, A
Tuesday's child is full of grace,A
Wednesday's child is full of woe,B
Thursday's child has far to go,B
Friday's child is loving and giving,C
Saturday's child works hard for his living. C
And the child that is born on the Sabbath day D
Is bonny and blithe, and good and gay. D
so it is AABBCCDD
So just look for that! But, if you gave us the poem we could help!