We need more refs, that is evident. It's hard for some of us to tutor people to ref due to how busy we can be. Therefore, I hope this can help.
These are kind of listed from most important to least.
- familiarize yourself with this: http://bmgf.bulbagarden.net/showthread.php?t=56302
- the Reffing Encyclopedia is nice, but the move, ability, and item information can be lacking; acquire the Smogon search plugin (Reffing Encyclopedia plagiarizes off Smogon anyway), searching for moves and abilities is quick and easy, a wealth of other battle mechanics information can be found here: http://www.smogon.com/dp/articles/
- time can be important in passing the ref test; familiarize yourself with common moves, most of them are the same thing just a different type/effect: Thunderbolt, Ice Beam, Flamethrower, Surf, Earthquake, Stone Edge, Psychic, Close Combat, Thunder Wave, Toxic, Will-o-wisp, Hidden Power, Taunt, Encore, Agility, Swords Dance, Nasty Plot, Rock Polish, Dragon Dance, Calm Mind, Protect
- keep the following in mind every turn for both Pokemon and you should be fine for the most part: Status Effects, Ability, Move, Item, Misc. Effect (SeAMIMe), do note that this is not the order those things are resolved
- make sure to mark any changes in a Pokemon's stats, and any additional effects it has on it
- always ask for Gender and Ability of a Pokemon and make sure it can actually have that Ability (and Gender I guess)
- make sure that the Pokemon learns that move, but don't take too long, again, it helps to be familiar with moves, Charizard obviously learns Flamethrower
- the proper way to handle an illegal move or ability is to tell the ref tester to select a legal one
- burn status halves a Pokemon's attack
- critical hits double the damage dealt after all of the following are ignored for the duration of the critical hit: the user's [Special] Attack drops, excluding burn, the target's [Special] Defense gains, including Reflect and Light Screen
- Leech Seed removes 12.5% from the targeted Pokemon, but adds however much is lost to the user; for example, if you Leech Seed a Blissey, you will get back more health than if you Leech Seed a Shuckle
- when a faster Pokemon uses Taunt and the other Pokemon uses a move a move that doesn't work under Taunt the same turn, that move will fail; after that, the Taunted Pokemon is unable to SELECT a move that doesn't work under Taunt until Taunt is gone, that means if the Pokemon attempts to choose a move that doesn't work under Taunt, the ref will tell them to use a different move, instead of the Pokemon using the move and then failing
- Hidden Power can only be 16 of 17 types! which one can it not be?
- Life Orb does not cause recoil when attacking a Substitute
- oldest trick in the book: Venusaur doesn't learn Stun Spore
This is the part where you can contribute. Make up any battle scenario, and it will be reffed and edited into this post. Specify any items and whether you want a certain something to hit or miss, and whether an effect should happen. Someone else or I will put the reffing in spoilers, so you can practice how to do it, and check yourself.
All calculations using 'old' calc
Post questions about reffing certain things as well, or offer other reffing tips.