I dont even worry about yahoo tbh , its one or two clicks a day is not worth the hassle, i have some auto run rss feed sites which rank stupidly well in yahoo but obviously sit around 50th in google because i suppose the duplicate content situation, they sit at around 1st ,2nd and 3rd in yahoo which generates 15 uniqes a day if im lucky, google is the one to beat , yahoo is pointless in my books.
However saying that if your niche is more cooperate and has the possibility of getting more business type of traffic then yahoo is used by many businesses i believe.
Sorry not much helpful advise just my 2 cents