Point of origin and shapes of spells

We will play combat on 5-foot grids. However, spell effects will be done via the template method for expediancy. If any part of a creature is in any part of a grid square that the spell template overlaps, the creature is affected in accordance to the spell description unless that creature has full cover (such as being completely behind a wall through or around which the spell can not pass or by being fully swallowed or engulfed in another creature).
Cone spells have their point of origin in or at the edge of any square the caster occupies. Therefore the caster can decide if they are in the effect or not.
Cube spells have their point of origin anywhere along the cube that the caster chooses. Note that the entire cube must fit in the room or space. The cube can not extend through floors, ceilings or walls. Cubes can not be down-sized unless the spell description says that it can be. If the entire cube does not fit in the area, the spell can not be placed there.
Spherical spells have their origin at the center of the sphere. Although these spells CAN be cast even if they do not fit in the room, the effects do not extend through walls, ceilings or floors unless the spell description explicitely says that they do. If you can not see the center of the sphere, you can not place the spell there.
Cylinder spells have their center at the center of one of the two circles of the cylinder. You must be able to see the center of one of the circles that define the edge of the cylinder or you can not place the spell effect there. The cylindrical spell can be cast if the height of the cylinder would go out of the room, but the effect does not extend through walls, ceilings or floors unless the spell description says that it does.
Line spells have their point of origin at one extreme of the line (often specified by the spell to be anywhere within or at the edge of any square the caster occupies). The entire line effect does not have to fit in the room, but the spell effect does not pass through walls, ceilings, or floors unless the spell says that it does.
Note that in all cases the origin of the spell must be perceivable (via vision or a vision alternative such as blind sight)  by the caster unless the spell says otherwise.  This means that if you can not see your origin point of the spell you can not cast your spell in that location.  
 (Note that this entire clarification is rules as written).