I have had recent occasion to observe young people raising their children and disciplining them (or not). One sometimes sees articles from a positive perspective about how children should be raised. "Make sure they know that you love them." "Take time to listen." "Instill in them a sense of wonder." My goodness, what rubbish that all is.
Being a negative and critical person, my responses are quite different. I watch young parents all the time, listening to what they say and thinking No, that won't work. I am guessing that this group will have had some similar experiences. I am curious what things you notice and what advice you would like to pass on in the form of No, that won't work. Don't be afraid to point out the obvious. Apparently even bright, educated, responsible, kindly parents miss the obvious. I often did. In fact, try not to stray too far from the obvious.
I will start. Do not offer a reward to a child beyond their time-understanding, which is usually minutes rather than hours. A promise of ice cream this afternoon if you will obey Mummy right now is meaningless to a young child. All they hear are the words ICE CREAM, which they then want, right this second, and screw you and your sitting still/finishing your carrots/lying down for a nap. It may even be a stretch for a six-year old*, unless you are intentionally trying to - gradually - teach concepts of time or delayed gratification. Ditto for removing a reward. Saying "You won't have any ice cream if you don't eat your veggieburger" is largely meaningless unless that ice cream is pretty much coming out of the freezer and into view right now. At which point you either get some veggieburger action or a complete meltdown.
*Hell, it's a stretch for adults, lots of the time. I'm thinking I might go and get some ice cream, which I shouldn't have.