the one thing that gets alot of people, especially n00bs, in guitarTIW is the 5 note combo. Now as some of you probably already know you cannot hit all 5 keys and get all 5 notes. To get all the notes, pay attention to the positioning of the notes and hit the first 3 then IMMEDIATELY hit the other 2. This takes some practice but will allow you to get the notes and rack up the points.
Hope that helps