This method was described by D.B. Wilson of Wilson & Alroy's Record Reviews in his essay "Toward A Technical Analysis of Song Lyrics". You do this by starting out with 75 points and then giving each line of a song's lyrics a score based on the following scoring table:

Example ratings by Mr Wilson include one verse each from Joni Mitchell's A Case Of You (105 points) and The Eurhythmics' Sweet Dreams (Are Made Of This) (18 points). Let me present an example of my own:

Paul Simon, Graceland, 1st verse and chorus:

The Mississippi Delta was shining
Simile, +4
Like a National guitar
Continued simile, +8
I am following the river
Down the highway
Through the cradle of the civil war
Metaphor, +4
Total: 91

I'm going to Graceland
In Memphis Tennessee
I'm going to Graceland
Poorboys and Pilgrims with families
Social consciousness, metaphor, +9
And we are going to Graceland
Contrast, +2
My traveling companion is nine years old
He is the child of my first marriage
Complex emotion, +10
But I've reason to believe
Trite, -5
We both will be received
Trite, -5
In Graceland
Total: 86

In my opinion, for obvious reasons, verse scores should be averaged, not added, to compensate for songs of different length. Have fun playing with this strange little scheme.