Definitely count down to any change - 10 minutes, 8, 5, 3, 1. Then stick with it. Be consistent with it so they get to know that you mean it, so they need to understand what "2 more minutes and then..." means.

I'm finding gentle discipline - quiet time to calm down, then sitting on my lap away from everyone else and asking "what's going on with you" (nicely, as an introduction to discussing what's bothering him) helps far more than time out / shouting (never works, often makes things far worse), etc.

Ask him why "no" upsets him so much. Obviously no one likes to be told they can't do what they want, but this seems to be a trigger all by itself. Ask him what he feels would be fair - I can do this with my son who is 7 as well. Sometimes he has an idea. Mostly I have to suggest things and then he will say if he thinks it's fair or not.

Like we got him a magnifying glass... what's the first thing a little boy wants to do??? I had banned him outright from trying to make something burn using the magnifier, but after I busted him doing exactly that, I realised it wasn't a fair expectation to set. I know how curious I was when I was little and how much "fun" it was to experiment and see what happens. So I told him new rules: he has to ask first, and someone has to be with him (mom or dad). He agreed that that was fair and so far we've kept to the deal

Obviously you can't do this in every instance but I think bending on a few things helps them react better when you can't bend on others. *shrug* maybe???