Magic in Red Ash is just another type of skill. While this is true there are a few addition features to these skills. First there are currently 3 main branches to magic with each representing a distinct type of caster.
Illustration of Der Zauberlehrling.
Original Source http://en.wikipedia.org/wiki/File:Tovenaarsleerling_S_Barth.png
A casting is where a caster selects a spell, sets the damage, range, or other variables to figure the MAP (and sometimes PAP) cost and begins the casting, committing the cost to it. When all the cost is paid in full the spell can be released, held or harmlessly discharged.
The number of rounds it takes to cast a spell depends on the skill level the caster has vested in it. With 1 level in a spell the caster can spend one MAP per round. So a spell that you will spend 10 MAP on will take 10 rounds to cast. With 2 skill levels in the same spell your casting time goes down to 5 rounds, and so on. Always round up with casting time, so 3 levels in the same spell will be ready to release in 4 rounds. Even an arcane must follow this rule at least for the base spell. They can then add to the casting as per there ability. Some spells have special rules on casting time. Most notably is undeath.
Once the full cost is paid a spell can be released. Releasing some spells requires a ranged attack on either a target or a space. You must roll to hit just like any ranged attacker would have too. Targets may also have a save to roll depending on the spell cast at them.
You can also hold your spell. This gives you an ability to release the spell as an interrupt action (see combat). While being held a spells control must be rolled if the spell has one.
You may also do a harmless release of the spell which will permit you to reclaim 1/4 the cost.
A Psyche caster also has the ability to pay a maintenance cost and begin casting a new spell. They can do this one at a time with an increased cost and control difficulty to all spell control rolls.