For a magic item to be effective it must first be activated. This may be as simple as picking a sword or a character placing a ring on their finger. Some magic items, like rings and cloaks, function constantly once they have been actived but in most cases magic items require a standard action to activate. This action does not provoke an attack of opportunity. Spell completion items, such as scrolls and wands, are treated just like spells in combat. This means that these magic items do provoke attacks of opportunities.
All magic items require a standard action to activate unless the items description states otherwise. For magic items that cast spells that spell has the same casting time requirement as the spell unless the item's description explicitlly states otherwise.
The four ways to activate magic items are described below.
Spell Completion Items
Scrolls are spell completion magic items. Scrolls contain a spell that is mostly completed. The preparation of the spell contained within the scroll is done the caster who created the scroll, so there is no preparation time needed before the spell is cast. In order for a character to utilize a spell completion item they must complete the casting in the form of final gestures, words, or other thematic triggers. Activating a spell completion magic item is a standard action, or the spell's casting time if that is greater, and provokes attacks of opportunity jsut as a spell does.
Using a spell completion item may be dangerous. If a character attempts to use a spell completion item for a spell that is not on their spell list and/or the character is not a high enough level to cast there is a chance that something may go wrong. If the spell completion item completes a spell that is on the character's spell list and the character is high enough level to cast there is no danger from using a spell completion item.
Spell Trigger Items
Spell trigger magical items do not require any gestures, nor do they require the spell to be finished by the caster. They only requirements are that the spell on the caster's spell list and that the caster knowns the activation word for the item. This even applies to characters that do not as of yet have access to spells, such as a low-level paladin or ranger.
The character must know the what spell is stored in the magic item before they can use the item. Activating a spell trigger item is a standard action that does not provoke an attack of opportunity.
Command Word Items
Command word magical items require the character to speak a specific word to activate the item. The character need not have the spell on their spell list in order to use these types of items. If the magical item does not mention that the item is spell trigger, spell completion, or a use activated magical item it is assumed to be a command word activated item.
While a command word magical item can be a common word, most of these items use an ancient or archaic language to trigger spell effect. Activating a command word activated item is a standard action that does not provoke an attack of opportunity. The command word to activate an item is written somewhere on the item. It might be hidden within a pattern or design carved into, engraved on, or built into the item. On other hand the item may not have the command word directly on item itself. Instead it may contain a clue as to the word might be.
Knowledge (arcana) and Knowledge (history) can be used to determine the command word for one of these items. To determine the exact command word for an item the character must succeed in a DC 30 skill check. If that result fails the character may make a second skill check (DC 25) to determine a clue as to what the command word might be. Detect Magic, Identify, and Analyze Dweomer all reveal command words if the properties of the item are successfully identified.
Use Activated Items
Use activated magical items must simply be used in order be activated. Potions, weapons, armor, and rings are all examples of use activated items. These magical items tend to be straightforward and self-explanatory in nature.
Most use-activated items are objects that a character wears. Magic items that continually function are almost always items that a character wears. Some, however, must simply be in the character's possession, meaning on their person. Some of these items made for wearing must still be activated. Although this activation sometimes requires a command word (i.e. a Ring of Three Wishes), most of the time simply mentally willing the magic item to activate is enoguh. The description of an item states whether a command word is needed in such a case.
Activating a use-activated magic item is either a standard action or not an action at all and does not provoke attacks of opportunity, unless the use involves performing an action that provokes an attack of opportunity in itself or the items description states otherwise. If the use of the item takes time before a magical effect occurs, then use activation is a standard action. If the item's activation is subsumed in its use and takes no extra time use, activation is not an action at all.
Use activation does not innately confer the knowledge of how to use the item, unless the benefit of the item comes automatically, such as from drinking a potion or swinging a sword.