(how) Do you know if your spells are successfull?

[Tr011]

Topic says it: I cast Fireball and see how my enemy dodges the attack. Ok, but what if I use Slow? Can I see if it was successful or not BEFORE my enemy acts again?
Would be useful to know so I can use slow i.e. another time quickened, what would make no sense at all if my enemy already failed his first saving throw.

RAI and RAW arguments are welcome :)

/edit: remember to say sources, so I can convince my DM to say me the results.

[deuxhero]

Slow would have some visual (remember turn basedness is an abstraction) of the foe moving slowly.

[BobVosh]

I'm vaguely aware of a rule stating that you know if your spells are resisted.
Found it:
http://www.d20srd.org/srd/magicOverview/castingSpells.htm#theSpellsResult

[NNescio]

I'm vaguely aware of a rule stating that you know if your spells are resisted.
Found it:
http://www.d20srd.org/srd/magicOverview/castingSpells.htm#theSpellsResult

Here's (http://www.d20srd.org/srd/magicOverview/spellDescriptions.htm) one that is a bit more explicit:


Succeeding on a Saving Throw

A creature that successfully saves against a spell that has no obvious physical effects feels a hostile force or a tingle, but cannot deduce the exact nature of the attack. Likewise, if a creature’s saving throw succeeds against a targeted spell you sense that the spell has failed. You do not sense when creatures succeed on saves against effect and area spells.

Slow (http://www.d20srd.org/srd/spells/slow.htm) is a targeted spell.

[Tr011]

Thank you all very much. It will help me a lot.
It will make the use of Call Forth The Beast (HoH) really funny.