we have 3, dd1, then 2 ds.
they're a bit older (15, 12 and 9).
as PPs have said, recognise the triggers. dd is horrendous when she's hungry, or tired, or hormonal (which is basically 100% of the time at the moment).
we kind of have to think of the DSs like dogs, that need a run at least once or twice a day. if they get that, they're much calmer.
also, we fill their evenings with as many activities as possible. boredom is the worst thing in our house for causing bad behaviour.
as for the arguments and bickering, i'm interpreting this as a sign of self-confidence - they're all comfortable standing up for themselves, and their own feelings (even if that's with us!). i could be deluded, but that's what i'm hoping.
if any of them stopped arguing back, and caved in, then i'd be even more worried.
finally, i'm not sure i want placid, unassuming children. i have regular interactions with lots of children (through coaching sport, and helping at cubs/beavers etc), and the quiet ones that wouldn't say boo to a goose are BORING! much rather have some cheeky ones to talk to!