Have you got an agreed list of sanctions/consequences Hothead? We found it really helped for ds to know what the consequences would be for certain things.
The standard consequence is deducting 10 minute of his computer time, but if he gets up to three of those it basically means he has not intention of adjusting or stopping his behaviour - then he loses the lot.
We also have zero tolerance - no warning, straight to full loss of computer time - for breaking things or hurting, but actually he's never violent, so we haven't really needed to use that for him. We have had to implement it for ds2 on occasion though, when he's lost his temper and hit ds1 after having been pushed too far.
Same rules apply to everyone in the house, so there can't be any accusations of favouritism and everyone knows the score.
We sat down together as a family to agree and write a list of house/family rules. We used to have it attached to the front of the fridge, but everyone knows them by heart these days (ds1 is 10 now). From that list we discussed and agreed the sanctions and what would happen when the rules were broken. In the early days it really helped to have it there as a visual reminder and to be able to use it to refer back to and reinforce the rules and consequences regularly.
I tended to find that prior to the rules list being created, I was giving out adhoc sanctions based on whatever was going on that day and that tended to either escalate things or ruin everyone else's day if it was something like 'right because you've done x, we're not going to go to the park'.