Magic: Spell Points
All Casters--whether Arcane or Divine--use his method for determining their spell points. They get their modifier (Int for Wizards, Wis for Druids, etc) times the level they have in the class that grants them spells.
For instance, a 1st level Sorcerer with a Cha of 20 will have 5*1 = 5 Spell Points.
A 15th level character With an Int of 20 that has 5 levels in Wizard and 10 levels in a class that only grants advancement in spellcasting every other level (Such as Blood Mage) Will have 50 Spell Points, NOT 75.
Note that this is not affected by caster level changes such as from the Practiced Caster Feat, et cetera. Those Feats are meant to improve how the caster casts spells, not how many they have access to.
Spell Cost:
The Cost of Spells is as Follows: It is Equal to the level of the Spell. Yes, this means that they have unlimited 0 Level Spells. It is not unbalancing to the game for these minor spells to be cast at will.
Sorcerer and Favored Soul Caveat:
To keep these classes worthwhile and to keep the balance in the game, Sorcerers and Favored Souls have half the cost as other classes when casting spells. Just like in a normal game, the point of these classes is to be able to cast a LOT more spells with the restriction of only having a few ever to choose from. This means that a 1st Level Favored Soul casting a Bless Spell will only use 0.5 Spell Points to do it (Yes, Fractions are possible; if it is easier for you math wise, simply double the number of spell points that you have and apply the standard spell cost; this works out exactly the same).
Spells Known/ Spells Prepared:
Use the spell charts in Pathfinder appropriate to your class to find the number of spells known as normal for a Spontaneous caster. For a caster who has to select their spells ahead of time (Everyone who isn’t a Favored Soul or a Sorcerer), select which spells you have access to for that ‘rest period’ at the beginning of the day. Apply the Modifier Bonuses as normal for the daily memorization (For instance, a 1st Level Druid with a Wis of 20 will have three 0 level spells [base from the class] and three 1st level spells (one base and two bonus for having a high stat).
How This Works With Spellcasting:
Say the same first Level Druid chooses Cure Light Wounds, Entangle, and Endure Elements for her Spells for the day (a pretty typical choice). Whenever she spends spell points, she has those three spells to choose from (remember she has unlimited 0 level spells). She can cast those spells in any combination, as long as she has spell points to do it. If she casts five Cure Light Wounds and is out of spell points, she cannot cast anything higher than a 0 level spell, even though she chose other spells that haven’t been “cast yet”! If a modern analogy helps, think of Spells as the guns that you are using and the Spell Points as the total ammunition that you have between them (Assuming of course that they all take the same kind of bullet—but I digress). Once you are out of Bullets, it doesn’t matter that you have other guns.
Metamagic Feats:
These work just like normal; the Spell Point Cost is equal to the adjusted level of the spell. i.e., a Fireball (3rd Level Arcane) that has been Maximized (+3 Level adjustment) will Cost the same as a 6th level spell. Note that, just like with spell slots, you cannot increase a spell cost beyond the max level you are capable of casting (A 1st level Sorcerer cannot heighten a Sleep Spell to 5th level, for instance).
