Summoning: What is specified as you begin casting? What if things change?

[Hiro Quester]

If I'm playing a druid, summoning in a nature's ally.

I get to specify which creature I try to summon, and where it is placed on the battlefield.

How much do I specify when I begin casting? How much of the spell's effects can I adapt to the circumstances of the battle as it now is, on my next turn, when the spell completes?

For example, if the party is about to be attacked by a group of enemies, and I decide that summoning a Nature's Ally using SNA IV would be a good way to kill or grapple to ineffectiveness a particular enemy. I use my turn to start summoning.

But what if that particular enemy moves or is killed during that turn? I might want a different creature from that spell's list, or a different location for it to appear.

Three possibilities:

During my first round when I begin summoning, I declare what I am summoning, and where I want to place it. ("I'm summoning a giant crocodile to appear in this location here." At the beginning of my next turn that creature arrives there, no matter what has changed during that round.
My first round I spend casting the spell specifying what creature I want to summon ("I'm summoning a giant crocodile"). When the creature arrives on my next turn, I specify where I want to place it ("The crocodile appears in front of this enemy and bites him".)
First round, I declare that I begin casting SNA IV. On my next turn I declare what creature I summoned, and where I want it, based on the battlefield as it currently is.

I have been playing it as #2. Another player in our group seems to play it as #3.

How do you play/DM this?

[Karnith]

Per the SRD: (http://www.d20srd.org/srd/magicOverview/spellDescriptions.htm#castingTime)

A spell that takes 1 round to cast is a full-round action. It comes into effect just before the beginning of your turn in the round after you began casting the spell. You then act normally after the spell is completed.

...

You make all pertinent decisions about a spell (range, target, area, effect, version, and so forth) when the spell comes into effect.

So, I've always played it as option #3 on your list.

[Hiro Quester]

Oh. That's even better. Thanks, Karnith!

So if the battlefield changes during the round I spend summoning, I can change from my original intention of summoning a giant crocodile to summoning 1d3 lions, and can change the location of summoned creatures.

I always wanted to do that, but thought it would be cheating to change my mind during the summoning round.

[Ger. Bessa]

I think it pretty much depends on the DM. For exemple if you suddenly need to be protected, you could summon Orcus instead of the alligator. Especially if he thinks you're a cheating problem player.

[Andezzar]

I think it pretty much depends on the DM. For exemple if you suddenly need to be protected, you could summon Orcus instead of the alligator. Especially if he thinks you're a cheating problem player.Please remind me which SNA/SM list Orcus is on. Unless Hiro Quester is playing in Jedipotter's group, I don't think Orcus will show up randomly.

[Urpriest]

Please remind me which SNA/SM list Orcus is on. Unless Hiro Quester is playing in Jedipotter's group, I don't think Orcus will show up randomly.

I think that was the joke...

[Andezzar]

Me too, I just wanted to acknowledge the origin of the joke