If you read and, closely, follow Robin2's simple rf24 tutorial you should be able to get them working. That tutorial sure helped me. The code in the examples has been proven to work many many times. If it does not work for you, there is likely a hardware problem.
Run the CheckConnection.ino (look in reply #30 in the tutorial) to verify the physical wiring between the radio module and its processor (Arduino).
It is very important that you get the 3.3V supply to the radio modules to supply enough current. This is especially true for the high power (external antenna) modules. Some have success with a 10uF to 100uF cap across the rf24 module power pins. I use homemade adapters like these. They are powered by 5V and have a 3.3V regulator on the board. Robin2 also has suggested trying with a 2 AA cell battery pack.