[hashkb]

Don't forget the unbreakable criteria:

<= 3:30; shorter is better

No more than three verses made of at most two straight-rhyme couplets.

Repeat chorus at least four times, more is better.

Keep all instrumental interludes short and simplistic. Cliche pentatonic guitar solos only.

Edit: almost forgot the most important one: be hot, use your body to sell the music.