I'm an instructor in training and have helped out with the practical portion in a PAL and RPAL course, so I'll try and give you a couple of tips that haven't been mentioned yet above (which all the stuff above I agree with 100%, so bear it in mind in additoin to what I'll write here).
Are you challenging the tests or taking the full classes followed by the tests?
If you're challenging, I would suggest you go to a store like Wholesale sports and have them show you in particular a semi auto shotgun and how it is loaded/unloaded (that one seems to trip people up fairly often if they've never handled them before) and look at a lever action rifle and learn how the half #### safety on it is set... otherwise the PAL test is pretty easy, especially if you're taking the class since everyone gets a chance to handle each type of firearm on the test. You very likely will see an example of each kind of action and have to show how to handle, load, unload and prove safe each one. ABOVE ALL KEEP YOUR FINGER OFF THE TRIGGER, unless you are lowering the hammer on a lever action rifle or something like that.
The RPAL one is a bit trickier, but fairly similar. The toughest part for people who haven't shot pistols is keeping the muzzle pointed in the safe direction since pistols are so short. When people have trouble getting the slide to lock in place on the semi autos they quite often end up pointing the muzzle at themselves or the instructor--- don't do that. Understand and be able to explain what happens when you squeeze the trigger on a single action only revolver, double action only revolver, and a single/double action semi-auto pistol as there are questions on the written exam and on the practical about that. I really feel the best way to pass a practical exam is to get out and shoot the different types of pistols, not play with them in class, so if you have the option of doing that take the time to do it.
Learn the different types of bullets and be able to identify them ie: full metal jacket, wadcutter, hollow point, round nose, soft point, etc, that will be on the test for sure. Bear in mind that the caliber ISN'T always stamped on the head of ammo, (like in the case of rimfire cartridges) but it usually is.
If you've spent time around firearms you should pick all this up fairly quickly and do fine. Good luck!