General GMAT Questions and Strategies | Re: Just took my first GMAT - 640 (Q44, V34, IR 4) - any advice?

Hey darkknight, NJ native myself. I can certainly relate to your uneasiness with combinatorics/probability problems. While the underlying theory never changes, the methods of application are wide ranging and sometimes dependent on very minute variations in wording (and thus implied meaning). I never found just one resource that did it all for me (not saying that one doesn't exist though!), but here's my suggestions:

1) GMAT Club Free Math Book - there's a section on combinatorics/probablility