I didn't read up on it but just used it...still works and my DS is 12yrs old now!...I've never got to 3 yet and to be honest I'm not sure what happens if I ever did!!! lol
Basically, you warn them about the 123 being needed and this is the 1st warning of there being an issue....(sometimes this is enough to get compliance or remedy the issue) ....you are using 1 as a first warning to comply, 2 is you're pushing too far and the consequences will not be pleasant if you don't comply...and 3 is when you are beyond that point/chance to comply and a punishment is delivered...obviously the punishment has to fit the crime and needs to be short lived, immediate and realistic in delivery...no point in threatening to ban things for days, stop a visit out somewhere fun...make it things that are in the moment/day that are easier to implement and don't create another area of difficulty...eg, you won't be watching favourite prog when we get home, or you cannot have your 'whatever', toy is fav at the time, no yummy pudding, no pc time...whatever is the most relevant thing at the time and within that day...short and quick and not carried on longer....depends on the crime too and has to be equally founded...not overly unpleasant but unpleasant none the less...it's about removing priviledges. It's also about not liking the behaviour and not about being a bad child...it's never the child and only the behaviour at that time iykwim
That's basically it...you explain what the 123 is for...that 1 and 2 are the only chances that will be offered and 3 will mean a punishment...then you stick to it!
I only ever used 123 when I actually recognised the situ was creating a difficulty and my reasoning was having no impact, so it's not used too much and doesn't apply to everything, just the important things iykwim