In my campaign I've been requiring characters with Arcane Backgrounds to determine how their powers are manifested. In addition to deciding the trappings of each of their powers, I've asked them to choose from a lit of "activation methods".
All characters with an Arcane Background should choose one of the following activation methods. Optionally, a different activation method can be selected per power.
Words: The character cannot use his powers if silenced or unable to speak. Even if the character whispers there is a chance his spellcasting will be noticed – make a Stealth roll, opposed by Notice.
Gestures: The character must use his hands to activate his powers. Normally, he uses both hands, but he may attempt to use only one hand at a –2 penalty (and at an additional –2 if attempted with his off hand). The character can make a Stealth roll, opposed by Notice, to make the required gestures without being seen.
Materials: The character's powers require some kind of material components (the details may be specified if desired). These materials must be purchased in advance, and are consumed at a rate of $1 worth per Power Point spent. The character must have at least one hand free to access his components.
Focus: The character's powers are channelled through a specific object which the character must be holding in his hand. If the object is lost or destroyed the character cannot use his powers again until he regains it or spends a whole day attuning a new focus.
Concentration: Using a power consumes the character's entire action; he cannot take any other actions while doing so. In addition, he may only move half his Pace in a round in which he is casting.
Music: The character must be able to sing or play an instrument to activate his powers. His music cannot easily be concealed, and is audible to all within range (or 5” at a minimum).