I see in the Beastiary that some creatures have a movement speed that is listed as, for example, Fly 60 (Perfect). But I can't find any explanation of what it means by "perfect" (or good, or average, etc.) I'm sure I must be overlooking something obvious...
If you look under the Fly entry in the Core Rulebook, it lists the maneuverabilities and associated penalties/bonuses. I don't have them memorized, but I know that's where they are.
Fly skill, page 96:
"Creatures with a fly speed treat the Fly skill as a class skill. A creature with a natural fly speed receives a bonus (or penalty) on Fly skill checks depending on its maneuverability: Clumsy –8, Poor –4, Average +0, Good +4, Perfect +8. Creatures without a listed maneuverability rating are assumed to have average maneuverability.
A creature larger or smaller than Medium takes a size bonus or penalty on Fly checks depending on its size category: Fine +8, Diminutive +6, Tiny +4, Small +2, Large –2, Huge –4, Gargantuan –6, Colossal –8."
Please note that creatures in the Bestiary already have such bonuses and penalties calculated into their charts; for example, a Bat (Familiar) is an Animal with 1 HD and Int 2, so it has only 1 skill point; if we examine his Skill bonuses, we find that:
Fly +16 = Ranks 1, Class Skill +3, Dex +2, Diminutive +6, Good Maneuverability +4
Perception +6 = Ranks 0, Wisdom +2, Racial +4
So, you don't have to add (or subtract) these bonuses from creatures already in the Bestiary; however, if such creatures change size, or you create new creatures as GM by yourself, you use these guidelines.
Just my 2c.