You have covered most of the required advice, Roddybug.
In your example, Garnet, you have a “base class” (one that you can take at level one)- the Cleric, and a prestige class (a class that has prerequisites)- the Champion of Torm.
The CoT requires your character to be non-evil, have a BAB of +7, and to have a Weapon Focus feat in a melee weapon. Your cleric/CoT would have to begin first level as a cleric; choose or become a non-evil alignment, pick up a Weapon Focus
feat (at level 1, 3, 6, or 9); and raise her BAB to +7 (level 10 cleric).
So the first 10 levels of your character cannot be anything but cleric if you are using only those two classes.
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