I always find the most difficult thing is getting used to where the offside of the car is when it's on my right rather than my left. The actual rules of the road sink in very quickly, but it takes me a day or two to get into positioning the car the right sort of distance from the side of the road - and more importantly from parked vehicles. That, and constantly forgetting that the gear lever is ON THE RIGHT -I'm forever automatically dropping my left hand to find myself trying to change gear withe the door pocket.....