There is no special tricks to the Rescue Diver exam. It all boils down to knowing the material and applying it. This is a non-professional certification so any wrong answers will be discussed. It is actually hard to fail the written portion (assuming you have some idea what you are doing).
The practical portion is hard (or should be). In a real life scenario there is a lot more stress and that can affect the way you behave. The cannot create a real accident and you will always know in the back of your mind that no one is REALLY in danger. For this reason they will use other techniques to stress you physically and mentally. For my training the first day was practice with the opportunity to ask questions and get guidance from the instructor. On the second day we were on our own. As emergency scenarios unfolded the instructor would point to one of us and say, "You're in charge." Various people would then play their part. Some were victim, some were there to help, some were they to interfere and some didn't know what was going on.
The most important thing is your safety first. If you don't make sure you are save first, they will show you your mistake (had a very large Course Director jump on me and attempt to rip my gear off, with surprising speed; fortunately my instructor prepared me for that in the pool).
The second hardest thing is keeping safe, steady breathes. Once you have the victim on the surface and bring them back to shore (a) don't dunk them underwater and (b) make sure you keep the breathes regular. It is more important to take longer to get everyone's gear off and keep steady breathing. At first, I'd get a steady rhythm breathing then start focusing on getting the gear off.
Third, don't assume they are not breathing. Check for breath sounds first. Don't bother checking for a pulse. If no breathing, assume no pulse.
As with all diving... don't panic.
