I have been learning N4 verb group.But I don't know sure how to divide words group by seeing.So I memorized group I,II,III by heart.Although I still trouble in dividing because I can't memorized all.So is there any easy way verb to divide group I,II,III respectively on seen ?

    Text Book says
>　いきます(Group I)
>  ねます  (Group II)
>  きます　(Group III)

I am not clear about group seperation？Is there any group making guide ?