Winternight said:
I cast charm person on a fighter. Does he KNOWS that they have been charmed?
No. Assuming he saw you cast, he knows you have cast a spell on him, but because he's
charmed he sees that in the most favorable way possible. You're his good friend, so of course you wouldn't cast any harmful spell on him, therefore whatever spell you cast must have been useful.
If your target has ranks in Spellcraft, and makes his check to identify the spell you cast, then he knows you cast
charm person. Even in that case though, he sees you in the most favorable light. He knows he has been
charmed, but he doesn't care, because you're his good friend and he thinks he'd feel the same way even if the spell were not there.
If he succeds his save, does he know I have tried to charm him. Can he react on that?
The fighter does not automatically know what you tried. He knows he resisted a magical effect; if he saw you cast, he probably assumes you're the one who tried to cast on him. He may be suspicious, but since he has no magical training, you can lie about what you were casting.
Again, anyone with Spellcraft who sees you cast (including the target) can make a Spellcraft check to identify your spell. If successful, they know you attempted a
charm person. Even allies will probably be upset with you at that point.
If he doesn`t succed his save and reacts as I want (holds off the dragon for just some rounds). now the charm person wears off. Does he know he didn't really wanted to fight the dragon?
In most cases, yes. Presumably you're his enemy, or at best a stranger, so he wouldn't normally follow your orders. When the spell wears off, he'll wonder why he was feeling so friendly toward you. Only the stupidest characters would fail to realize you had used magical influence.
Someone who has been
dominated definitely knows what happened, because that effect directly overrides their mind and personality. The spell does not remove the memory of having been controlled.