Just remember, when adding templates, stack them in the proper order.
The Type Pyramid
Some creature types are easier to change than others. Some types, such as undead, cannot change(with a few, rare exceptions). As an aid to determining the type of a creature with multiple templates, we can arrange the types in the form of a pyramid. At the base of hte pyramid are those types that can be changed most easily. At the top are the types that can be changed only rarely, if at all.
Purpose of the pyramid
Usually, the last template applied determines a creature's type. However it is possible that some template imposes a creature type that overrides any following templates. Types higher on the pyramid override lower types, even if the lower type is applied afterward. You can apply the half-dragon template to an earth elemental, for instance, and it remains an elemental. The pyramid is about creature types, and does nto dictate the order in which you must apply templates.
The Pyramid from Base to Top.
Animal, Humanoid, Vermin.
These types form the base of the pyramid. these are the simplest creature types, with the fewest exotic abilities. Almost any template applied to them overrieds their type.
Magical Beast, Monstrous Humanoid
These two types occupy the level above the base, a narrow band between humanoid, whos type they override, and more exotic types such as aberration, fey, giant, outsider, and humanoid(shapechanger), whos type override theirs.
Fey, Giant
These two types occupy the level above magical beast and monstrous humanoid. While they override animal, humanoid, magical beast, and monstrous humanoids, other type s override theirs.
Dragon, Humanoid(shapechanger)
These two types occupy the level above fey and giant.
Aberration:
This type sits alone at the level above dragon and humanoid(shapechanger).
Elemental, Ooze, Plant
These three types occupy the level just below the top. If some other templat is applied to them, they generally retain whichever of these thre types they have.
Construct, Outsider, Undead
These three types reside at the top of the pyramdi. Once a creature becomes an undead or construct through the application of a template, it cannot become something else. Once a creature stops being a native of the Material Plane, it becomes an outsider and stays one.
Keep in mind this is a 3E(not 3.5) book. Especially in regards to the Outsider bit at the end.