Im into the darker spectrum of yaoi, Fluffy ones are also great but my tastes always lead me back to "the dark side" ;)
Another thing i look for is POSSESSIVE SEMES!!! Ahhhh!!!! Gotta luv dem possessive semes(づ ̄ ³ ̄)づ
Last thing, i also like the rich x poor situations more specifically rich seme x poor uke ones, then the seme provides and...... reply