Jellybrain - I actually think ds is MORE hyperactive now since starting school! He's certainly harder to control, I find. Triggers seem to be transition times, being interrupted when he's focussed on something, involvement with other children etc, though those things don't necessarily trigger tantrums, just an increase in his uncontrollability and 'off-the-wall-ness'. Coming out of school is a nightmare - he runs away from me, back into school to disrupt the after-school club, throws his lunchbag and water bottle around etc. Even the teacher can't control him at hometime. Off the school grounds he picks up litter, sticks etc and throws them around (sometimes at other people), shouts rude words all the way home (sigh). His behaviour can change instantly when another child appears on the scene, eg when I took him out in the street on his bike last weekend, he was fine when it was just him and me but when a boy that he knew passed he started picking the bike up and throwing it around. So you see, it's not really tantrums but worsening of general behaviour problems.
As for strategies ... they change with the weather, tbh. What works one day might not work the next and vice versa. Generally I have a combination of star chart for positive behaviour and each point represents 10p towards the week's pocket money, and a token jar from which he's fined for anything inappropriate. The token jar is great because there are so many stages to it, eg I ask him to do something, he refuses, I ask again, he refuses, I TELL him to do it, threaten to count to three, START to count to three (with the understanding of what happens when I reach three), then I take away a token without repeating the reason why. There's no need, he already knows. If he gets upset at losing a token I remind him that he can earn it back if he wants to. I think the type of tokens you use matters a lot - the pasta jar wouldn't work with J because he hates pasta! - so we're using shells and coloured glass shapes.
If he gets into a real paddy I find the best thing is for me to stay calm, acknowledge that he's angry and explain that we can talk it through when he's calm. I've taught him to try counting to ten and breathing deeply, but he's not too happy with this because he expects everything to be right again by the time he reaches ten, but of course it isn't so it upsets him all over again. I also remind him of what the 'reward' will be for calming down and complying with my request, and he'll always get a point on his chart for coming out of a tantrum.
I also use forthcoming events as a carrot - tonight we're taking him to a basketball match (with tickets he won for full school attendance) and I've been dangling that one all week.
It's all based on positive reinforcement really, but sometimes it works and sometimes it doesn't. For that reason I never threaten or promise something I don't want to follow through, because consistency is incredibly important.