The official MCAT guide outline does not show any right hand rule at all and I never see it in any AAMC test. Any one had it in real MCAT?
Oh, when I read the OP i thought he was asking about the right-hand rule regarding magnetic fields. I think this is a lot more likely to be asked than the right-hand rule to solve for cross product.
I think both are pretty easy to learn, so it wouldn't hurt to learn them. I don't think the test will ever specifically ask questions on the right hand rule per say(i.e. which direction does your finger point), but rather a topic on physics that can be answered using the right-hand rule or with physical intuition.
I had one on the 7/16 MCAT, although it could have been an experimental question. It's not too bad, here's how I do it.
Take your right hand and point your 4 fingers towards the first vector. Then bend your fingers towards the second vector (bend them in the way they normally bend, not a crazy contortionist configuration). The direction your thumb points is the direction of the cross product resultant vector. It will be perpendicular to both vectors, and its magnitude is the length of the two vectors multiplied by the sine of the angle between them (unlikely to be tested).
For example, East cross North is up (out of the map if you're looking down on one). West cross North is down (into the ground/map).
For North cross South the resulting product has a magnitude of zero, since these two vectors are parallel (sine of the angle between them = 0).