Are you talking about the Summon Monster spells?
1. They don't summon daemons. There are some devils and demons on there, but no daemons. If you want to use these spells to summon daemons, you'd have to talk to your GM to add some appropriate daemons to the summoning lists. Note: demons are not the same thing as daemons (but the words are pronounced pretty much exactly the same way).
2. No matter what you summon with Summon Monster spells, there is no bargaining. You just summon them and turn them loose on your enemies. The bargaining comes with certain other high-level spells like Planar Ally or Gate where you actually bring them permanently to this plane and bargain with them to serve you.
There is a specific summon spell for that low level daemon that crystalizes souls.
Really, it is just a round about way of doing a spell that seals an enemy's soul in a gem. Not necessarily a guarantee, but it will tell you when your GM bothered to rez a former BBEG because the gem gets broken if the opponent uses a powerful enough caster.
Anyway, what usually happens when you summon daemons (not the basic summon monster spells- they are generally safe; I mean full on planar ally and such) is that they play nice until they find a chance to utterly destroy you and all you love.
Demons can be bargained with, since you just need to give them a good time (drugs, sex, and violence) and they are satisfied. And devils are famous for their deals.
Daemons though....they are nihilists seeking the destruction of all of creation. They can pretend to play nice...but they would love to break down a summoner with the pride to think that they can be controlled. Manipulation of trust and break down of realationships is their bread and butter. The only way you can hope to placate them into a deal is to offer them enough death, destruction, and souls in order to keep them busy. So only take this route if your plans involve the words like 'massacre', 'plague', or 'genocide'