21 month old's behaviour - not sure what to do

[anchovies]

I have 2 ds's eldest is 3, youngest is 2 in March. Ds1 was (and still is for the most part) a model child. Ds2 on the other hand is the complete opposite. He bites, hits, throws, screams and doesn't listen to a word we say but to be honest he is very charming with it which has meant that he has got away with a lot in the past (too much I think). So we are at our wits end. He is very bright and understands exactly what we say (i.e. no, reasoning, distraction or whatever) but just laughs and carries on. Shouting definitely doesn't work (nothing fazes him). So we need some ideas please. What do toddlers this age understand? Can anyone recommend a book with ideas?

Sympathies fellow toddler wrestler. I think at 2 years old both you and he are learning about what works in terms of behaviour. It's all a bit of an experiment. My current approach (which may well have changed tomorrow) is to decide what is completely unacceptable (hitting, biting, lobbing toys) and do one warning, then time out - just a couple of mins with me holding him until he's calm - then a kiss and a cuddle and move on. For minor transgressions chez mcnoodle I grit my teeth and try to ignore as far as possible (especially if distraction, explaination etc have failed). I don't think he's old enough to understand any system of reward/punishment, nor do I want to go for the full naughty step approach. But I think time out gives you both space to calm down. Am sure you've done all this. Have you tried Toddler Taming by Christopher Green (it's a bit harsh in places but he does have a practical, humorous take on the whole thing).