I've found getting in to reverse difficult at times, too. It doesn't make certain tasks, like parallel parking, very easy, but try this. Before shifting in to reverse, hold the clutch in for two or three full seconds before you try to put it in to gear. Since the car is at a stand-still, you don't want the transmission moving either, and holding the clutch in longer will let all of those spinning parts slow down and engage. Remember, reverse gears aren't cut and syncro'ed the way the forward gears are, and the higher warm-up RPM's only make this problem worse.
You may have some of the other problems mentioned about the clutch, but give this method a shot. It works for me and I'm pretty sure I actually read it in some owners manual somewhere.
