There are 3 primary types of magic. Prepared casting, Tacit casting, and Supplicant casting. Basically take Predictable, Reliable, and Fast: Choose 2.

Casters are not limited to one type. Anyone can access prepared or supplicant casting. Many simple prepared spells are widely known through the general populace, such as light and messenger spells. Some patrons grant minor magics to all in their domain. Tacit casting usually takes some innate magical affinity to access, but many have discovered these abilities through intense meditation or certain traumatic or magical encounters.

Prepared casting is a scientific approach where wizards carefully research the effects of their spells and carefully implement them using precise arcane formulas on surrounding magical energies. Prepared casting is Reliable, Predictable, but not Fast. Wizards may have a limited magical effects prepared ahead of time, but cannot modify the effect after preparation.

You may cast spells using Careful. For simple magic effects, you must create an advantage to prepare the spell. You must spend an invoke without gaining the +2 bonus to cast the spell. For more complicated and powerful effect you may attempt ritual casting. Describe what you want to do, the GM will state the difficulty and requirements for the ritual.

Tacit casting is when sorcerers control magical effects purely with intuition. Tacit casters generally lack the more in depth knowledge of the actual underpinnings of the power they control, but can often quickly adapt to new situations. However it can often result in unpredictable or uncontrollable effects. As such there is a bit of a stigma against it in the magical community and it is restricted in some places. It is Reliable and Fast, but not Predictable.

Supplicant casting is when clerics beseech their patrons for magical power. The clerics are not so much casting the spell directly as they are acting as a conductor from the patron who is the true source of the spell. However, the caster must rely on the benevolence of their patron for the effect to take place. If the caster is not following the wishes of their patron, they might experience lessened or even be completely cut off from their magic. Sometimes the supplicant caster might also be cut off from their patron. Supplicant casting is Fast, Predictable, but not Reliable.