Effects on the attacking Pokemon are applied before weakness and resistance. Effects on the defending Pokemon are applied after weakness and resistance.
Source: PUI Rules Team (2009-01-15)
The contents of your deck are technically unknown. If an effect calls on you to search your deck for a specific card or category of card, you may choose not to find a card, even if it is present in the deck.
Source: Worlds 2006 PCL Announcement (2006-08-18), PUI Rules Team (2008-05-08)
The game has no knowledge of the contents of your deck. For example, if you search your deck for something and fail, you can still use other cards or effects to search for the exact same thing.
Source: PUI Rules Team (2008-04-17)
An attack that copies another Pokemon's attack can only copy attacks printed on that Pokemon, not other attacks that the Pokemon may use due to Poke-POWERs, Poke-BODYs, Stadiums, etc. (with the exception of Lv.X Pokemon since they are considered "extensions" of the original Pokemon).
Source: PUI Rules Team (2008-04-17)
Benching a Pokemon removes all Special Conditions on that Pokemon including Poisoned and Burned, and all Attack effects on that Pokemon that do not place a Marker (such as Imprison).
Source: PUI Rules Team (2008-04-17)
A player must always have an Active Pokemon. There is no time in which they don't, not even after a KO. Replacement must be done immediately.
Source: PUI Rules Team (2008-04-17)
If a Retreat Cost is set to zero by an effect, it cannot be increased. Note this is different than a Retreat Cost that was reduced to zero by subtraction.
Source: PUI Rules Team (2008-01-31)
Mandatory game actions cannot be forgotten or missed; they must be done. Examples: Drawing a Prize card, checking for Asleep, etc.
Source: PUI Rules Team (2008-01-31)
Placing damage counters is not the same as doing damage. Things that add to or subtract from damage done do not affect placing counters.
Source: PUI Rules Team (2008-01-31)