Sophia this book is a systematic approach to managing children's behaviour. There is also a parenting course based on the techniques in the book. It was recommended to us by our social worker because DS1 has ADHD and ASD so his behaviour lags behind his age and he has other issues such as impulse control and meltdowns (which are basically tantrums). We use it on both boys and I can honestly say it transformed their behaviour. I could wander round Tesco with my perfectly behaved little boys feeling very smug about myself after applying these techniques. It also gives you a framework to use. I find that DH tends to get 'creative' with punishments so the boys might get their pocket money stopped or a favourite toy taken away. This gives you a system so that in the heat of the moment you don't react inappropriately, you just follow the system.
The first thing the system focuses on is play and how to play properly with your child without directing their play or forcing them to do things your way. It seems like an unnecessary part of behavioural management but it's actually important not to skip over it. We do two ten-minute sessions of 'special time' with the boys every week. During special time they get to decide what you do with them and it does not get interrupted to the point that if the phone rings you don't answer it. Once ten minutes is up special time is over, you can keep playing with then but you don't have to. Our boys love it because they are guaranteed parental attention and they get to be in control of the play. In terms of quality time with your children I think special time gives the most reward for very little time input. It makes them feel important to you.
The system uses positive praise and a reward system (star chart) to encourage good behaviour. It also starts small. In the supermarket example you might give a star for the child staying in your sight all the time rather than for 'good behaviour'. A toddler doesn't know what good behaviour is, they might think they've been good because they wanted to behave but in fact they've been a holy terror. So by giving very specific targets you can rapidly improve their behaviour over time.
The system of punishments is based on time out, one minute for each year of their age up to a maximum of five minutes. First you warn, then if they continue they get a time out. You also have consequences, e.g. If you don't eat your dinner then you will be hungry.
I have tried to summarise the system here but the book goes into a lot of detail and has troubleshooting sections for specific types of behaviour. Our biggest problem is getting the boys to get dressed and we have used a few different methods to work on that, the most effective one was a timer. If they got dressed faster than the previous day they got one star, if they got dressed in less than five minutes they got two stars. Stars can be traded in for rewards, e.g. fifteen stars for a game of monopoly.