I understand what you are going through. My husband is a big negotiator, and also can play "devil's advocate" very well - sometimes NOT requested. My younger child has picked up on this "negotiation skill" and CONSTANTLY tries her hand at it. Here's what I've found works:
1. When I tell YOU (child) to do something, I expect it to be done immediately. This IS NOT a negotiation or a request.
2. If you choose not to listen, you will go on your step/room.
3. Everyone in this house helps out - I cook, clean, do laundry, etc. You are expected to contribute since you are adding to the mess, eating our food, etc.
4. When I call you, you come immediately, AND say "coming Mom" so I know you heard me and you're on your way. (I do not accept, one minute, when the show's done, etc.)
5. If there's a problem, you are expected to use your words - not hit, scream, etc. I talk to you and I expect you to do the same.
6. We ask a question ONCE in this house. If Mom says "no" than that's the answer. DO NOT go ask Dad, because the answer will not change.
These are clear cut, often repeated rules in our house. I have asked my husband to back me up on these things. He has been EXCELLENT in telling our kids, "Go to your Mother right now." or "What did Mom just tell you?"
If you need additional incentive (for the kids) we use cut outs from Lakeshore Learning. I let each kid pick out one paper picture cut out (one picked a package of apples, the other cupcakes). I wrote their names on their pictures, then added a piece of magnetic "tape" to the back of 10 items. Now when we're having listening/following direction problems in the house I pull them out.
The kids "earn" a paper apple or muffin for good behavior, i.e. listening THE FIRST TIME they are asked to do something, getting dressed on their own, getting a school bag out, etc. The apple or muffin goes up on the fridge. When they earn 5, they get a treat (2-3 M&Ms) or get a t.v. show. If they earn all 10 by bedtime, they get special Mommmy or Daddy time, a trip to the store w/o sibling, lunch out, a sleepover with one parent in our bed, etc. Any bad behavior and they loose an apple or muffin. There is ONE warning before the apple or muffin is taken away, and they are told WHY it was taken away. Daddy helps by making a BIG DEAL out of how many apples/muffins are on the fridge when he gets home. (Can't take the credit. Got this idea from SuperNanny.) I find this "game" to be VERY effective when it's used off and on. If used too long, it looses it's charm.
Hope this helps you!
Sara
Mom to 2 kids - 4 yrs old and 3 yrs old