The principle I use to make normal songs jazz is:
On the different harmonies of a Key
Tritones:
I ii iii IV V vi vii
maj m m maj maj m dim
Expantion One:
I ii iii IV V vi vii
maj7 m7 m7 maj7 7 m7 7b5
Expantion Two:
I ii iii IV V vi vii
maj9 m9 m9 maj9 9 m9 9b5
Expantion Three:
I ii iii IV V vi vii
maj11 m11 m11 maj11 11 m11 11b5
Expantion Four:
I ii iii IV V vi vii
maj13 m13 m13 maj13 13 m13 13b5
On the different harmonies of a Key
Tritones:
I ii iii IV V vi vii
maj m m maj maj m dim
Expantion One:
I ii iii IV V vi vii
maj7 m7 m7 maj7 7 m7 7b5
Expantion Two:
I ii iii IV V vi vii
maj9 m9 m9 maj9 9 m9 9b5
Expantion Three:
I ii iii IV V vi vii
maj11 m11 m11 maj11 11 m11 11b5
Expantion Four:
I ii iii IV V vi vii
maj13 m13 m13 maj13 13 m13 13b5