Friendly fire on AoE spells, especially concerning the caster. What do you rule?

[Randomocity132]

Fireball, Entangle, Black Tentacles, etc.

If a PC casts this spell, and he's within the radius of the spell, do you rule that the spell doesn't affect him, or is he fair game unless the spell specifically states otherwise?

[Seerow]

He's fair game unless the spell says otherwise.

There's feats and class features out there that let you exclude yourself and allies from those sorts of things. Don't want to get hit by your own spell? Be careful where you cast it, or get sculpt spell or the like.